Placement of your AT cannons is critical here...
I find that putting one in the upper left section in the small alley in the bushes and then one on the bottom right long streetway is a good defense.
Also put some soldiers behind the upper right edge of the factory near the columns. If they can AT grenade the first tanks that come in... they all will get stopped in that section.
I find the boilers really hard to secure initially... mine as close to there as you can... AT and AP... most tanks will avoid primary streets mid town and just go rampant through the buildings...
Be sure to spread out your mines everywhere...

Heck... get 4 soldiers mining right from the get go...