When I force IG off and a bunker is sitting there, how do I destroy it? Many of my squads only want to walk inside of it, and I don't know how to force them to attack it.
You need some form of Artillery, like a PlasmaCannon for example, to ground-target it.
Or have a "big" unit, like Terminators, Ogryns, Walkers etc beat it up.
Can IG bunkers both be upgrade to repair/heal, AND have the explosive trap?
A Bunker can only have the repair OR the reinforce/heal aura.
But additionally to that the explsovie trap.
What damage types hurt bunkers best? Are they normal buildings, or do they have their own damage type?
Any form of Anti Vehicle Weapon I'd say.
Stuff like LasCannons should take down a Bunker in I'd guess 3 shots. .?.
Do bunkers have any other special rules that normal garrison doesn't (besides the IG upgrades).
They can be repaired, I guess.
If there is a heal/repair bunker that the IG has abandoned, what can I do to turn off the aura besides destroy it? Does it "flip" team after going inside it once?
Steal it.
If the Guard Player hasnt upgraded it yet you can actually do it, once you taken controll of it.
Atleast the repair and heal upgrade.