A few maps, such as Lenino, have a lot of AT guns in the movable configuration even though their placement makes moving them rather pointless (they start in a reasonable position and would need to be moved a long way to get anywhere new). The annoyance is that these movable AT guns are a pain to use - they can't turn and they slide around after every shot, requiring you to constantly switch to the movable position to correct the direction the gun is facing.
I think these movable guns should generally be replaced with the static version except when mobility is absolutely necessary.