Nah that was easy, I used to do a lot of modding for OFP and the first ArmA, and there were plenty of tools around to pick almost everything apart back then, and modders have made thousands of addons and mods where, besides original new content, there were heaps of them which featured many variations of the original content of those games, be it infantry, vehicles, structures, weapons, etc.
I made maps for those games where I'd pick their building models apart and adapted them in some ways to have more variation between them in the towns and cities, etc. Worked with guys in a mod team where they redid a lot of stock vehicles, armor and soldiers to fit another era/nation and so forth. And BIS would not have cared, as the mod community in those games was so important to the series' success too.
Of course, theorethically nothing is impossible, but I still reckon these chaps would have had a far easier job ripping off the TS content.. yet either way, I don't think Vstep will kick up much of a fuss if it was taken from SSE, since they did not create the models themselves anyway, but bought them.