is there any online multiplayer going on?
also, do infantry units operate in sqauds or are they single infanrtry units?

Infantry units are now non-dependant. You can make squads ,if you llike, like in any other strategy game (CTRL+'1' etc.)
I saw multi is based on Massgate, you can also use Hamachi.

As igor8472 said, multiplayer is through Massgate, which is up and running, and I've even joined a few games since purchasing this on gog.
Best thing about GC2 is that it supports campaign co-op play.