I plainly said to you that these units in coh2 are NOT designed to fight fortifications, because they don't exist in coh2.
Lets see what Relic has to say about the subject:
In game AVRE description:
"Churchill AVRE this special designed and protected Churchill AVRE (Armored Vehicle Royal Engineers) is equipped with a massive 290 Petard mortar that fires 40 lb (Flying Dustbin) capable of levering fortification or smashing troop concentrations."
So according to Relic there are fortification in game...
The units you mentioned are mostly stricktly infantry support units...
In game description Brumbar
SturmPanzer Brummbar known by its nickname "brummbar", this heavy assault gun has a 15cm howitzer in an armored casemate. It brings its gun into close range and smashes the enemy with 40kg
shells.
So according to Relic heavy assault gun exist and Brumbar is one of them.
Can we move on to something more constructive now pls...