Of course it can, they just have to take their time to do it. Several mods, like TC3, Ars magica , portal gun, has sounds, even musics, why IC² wouldn't? Their only problem would be excessive sound pollution from generators.
Difference is, IC2 has been around for alot longer than TC3, Ars magica, etc. but has bugged sounds, and has done for a long time. There was a patch for the 1.2.5 version I think it was which improved it, but it still seems strange that a mod with so many sounds, some playing alot (reactors :)), is unstable in doing so. Personally, an option to turn down/off the generator sounds separate from machines would suit me.
You can enable IC² sounds in config, they are disabled by default due pollution or another unknown reason. You can disable certain IC² sounds by deleting them from the IC² jar. IC² sounds are different as they are not downloaded somewhere and placed at resources folder, they are inside the IC² jar.