I set up a battle in which an Elite US Rifle Company with no heavy weapons or heavy explosives attacks a buttoned Conscript Panzer IVG, trapped by heavy buildings.
They were able to knock out the panzer, but not reliably or quickly. There did not appear to be any distinction between charging the tank (not move, fast, nor crawl) and a target order, save that moving troops were spotted and shredded by the Nahverteidigungswaffe.
The best time was 0'11'' to immobilize and 0'18'' to knock out, following a move order. Another test, also under the influence of a move order, resulted in them taking 0'19'' to immobilize, and failing to knock it out after 2'00'' (troops were ordered to move towards the tank again after the first minute). Average time with "Target" orders was 0'14'' to immobilize and 1'14'' to knock out. I'm guessing that each grenade thrown has a low, flat chance to hit and damage, modified by armor, resulting in the wide distribution of results.
I also note that the Panzer never bailed out, even when immobilized. They apparently do not consider unsupported infantry a serious threat. They also, unsurprisingly, were unable to spot stationary infantry in buildings. This may be why the Hotchkiss was unperturbed by my attacks. Unfortunately, I do not have a save from that game, and so cannot check if it was shocked.
I am unsure if range plays a role. However, I note that in a less scientific test, a rifle squad failed to damage a Lynx at 0m range over the course of 1 minute.
Are you thinking of the "Follow Vehicle" command of later games? It does not appear to be implemented in CMBO, and setting a waypoint on a vehicle does not appear to do anything special.
Thanks for the advice, and the link.