Engineers in Red Alert 2 can be used for these purposes:
To capture enemy structures. For this, an engineer was trained to be familiar with the standardized computer equipment present in most structures, particularly the master control terminal. The most highly trained engineers memorized blue prints of the structures, and then used small explosive charges to break their way in. During the Second World War, it would take five Engineers to break into a fully armoured enemy structure, but if it were damaged it could take less. By the Third World War, this was overcome by superior training and better explosive charges. These engineers were capable of taking over enemy structures almost instantly, but there was a price tag attached: these engineers cost over 4 times the price of a basic infantry unit. The Engineer was required to stay at the MCT and operate the structure from that point onward, but this did not prevent rival engineers from attempting to recapture the structure. Engineers could capture most buildings including power plants of any kind, Spy Satellite Uplinks, construction yards, tech buildings, and more. However, they could not capture turrets, Industrial Plants, cloning vats, naval shipyards, battle bunkers or tank bunkers. Only a Yuri Prime was capable of capturing these structures, excluding the bunkers.
To repair bridges. This was developed by the time of the Third World War. Engineers realized that they would have to repair bridges - floods and other problems, as well as enemy forces' destruction of the bridges, were often problematic. Fortunately, most bridges stored all of the tools for their own repair, except for a few the engineer carried, which allowed them to repair bridges very quickly. Unfortunately, the engineer would use up most of his supplies and tools in this way. Rather than journey out onto the battlefield without tools - and therefore without the ability to repair structures or capture structures, engineers wisely decided to stay inside the bridge repair hut - ostensibly to make sure that the bridges would not be damaged again, although in practice they were helpless to intervene should the bridge be destroyed - it would take another engineer to fix it again.
To repair allied buildings. Again, the engineer would go in, and use similar tools to the bridge repair hut to fix the structure. These tools and supplies would be used up in the process, and the engineer would wisely choose to stay in the structure.
To deactivate Crazy Ivan's bombs. For this, they had special pyrotechnic training. Once the bomb was activated, and engineer could deactivate it, supposing he could reach it at point-blank range. After that, is he would still be fully prepared to do other things. If the bomb is strapped on the engineer himself, he cannot deactivate it even though it appears that he can, requiring the player to train another engineer to deactivate the bomb on the affected engineer.
Engineers controlled by the AI have the following attack patterns:
2x targeting production structures, accompanied by 10 Conscripts
The Allied engineer is voice by Phil Tanzini, while the Soviet engineer is voice by Andy Milder. Tanzini would reprise his role as the Allied Engineer in Red Alert 3.
Soviet and Yuri engineers share their death cries, even though Yuri's engineers have their own in the game files.
Two Soviet engineer's selection quotes were cut, and are often restored in mods.
The Allied and Soviet engineers have an unused quote "We'll have the power up in 30 seconds, sir". Since no power-related voice messages were used in Red Alert 2, the Yuri engineer does not have this quote in the game's files.
In every first mission in the Soviet and the Allied campaign, the engineer is one of the key units, being placed second.
Since they're regular BuildingTypes, Naval Yards in RA2 can be captured by engineers if engineers can traverse Water (set MovementZone= and SpeedType= properly) or if a Naval Yard is placed on non-Water via map-editor (though in this case it'd be useless).
Selling or destroying a construction yard would produce the Allied engineer ENGINEER even when playing as a different faction.
This is because RA2 and YR "do not distinguish between factions". In TibSun and earlier there was no need to distinguish between faction-specific engineers since the factions all shared the ENGINEER unit anyway.
In the mission Free Gateway, the player receives "elite" engineers, which is not seen anywhere else in the Command & Conquer series among unarmed versions of engineers.
These Elite engineers are no different than Rookie/Green Engineers; Engineers have no veterancy bonuses coded whatsoever.
They're all part of the same team with VeteranLevel=2 so they could be sent with one plane and still drop an elite Tanya. A trigger forces them into Teams which come with a Script to change their House for that "early" MC-thing that doesn't happen to Tanya. Engineers have no VeteranAbilities or EliteAbilities defined, so they receive no veterancy bonuses
There are three Engineer units in the game: ENGINEER, SENGINEER, YENGINEER.
The result of this is engineers not always being selected properly when using 'T' if there are different Types (which shouldn't happen in regular gameplay). This not something modders can fix without using Ares DLL for the new GroupAs= flag.
A technique to fix it for the base game without engine extensions is called "Infantry Linking". However it is recommended no modder does this.
Allies can only build ENGINEER, Soviets only SENGINEER, Yuri only YENGINEER. This exclusivity was implemented with RequiredHouses.