If you want use rifle LMG as suppresion platform, you must activate it with hot key or with your mouse. After activating this, is your rifle squad immobile.
*inmobile*.... it can be deactivated and activated again whenever you want to. Lol.
Not exactly the situation you are referring too, but i once faced an double OkW team on Eindhoven were there was both a JT and a KT on the field ( one player going JT and the other KT).
Lateron, one JT was killed but another was called in again.
Eventho this wasn't what you asked for, it certainly was possible for the OkW player's to get multiple heavies on the field (including the aformentioned combo of JT and KT) in a 2vs2.
If you have an hour to spare or simply require proof, i recommend you watch the cast of it:
(the cast and game are quite good if i may say so).
Saw that on replay section weeks ago, you guys just pwned them, that Jagdtiger usage was pretty pretty bad.