To clarify, the air bags isolate the cab from the chassis.
There is also suspension between the axles and the chassis which is 99% of the time air on the rear, leaf spring front.
I haven't come across a cab that is suspension isolated from the frame of a conventional, even though the axles are on air. Theoretically as the driver is in the sweet spot of a much longer wheelbase, rather than sitting directly over an axle.
> I haven't come across a cab that is suspension isolated from the frame of a conventional, even though the axles are on air.
They are very often on a simple suspension. The cab will have a pivoting mount at the front and sit on air springs in the back.