I use area terrain bases for our terrain.
That said, you guys do have some nice terrain!
We use it for a lot of the terrain, although ours belongs to various members of our gaming group and some are more willing than others to base their terrain, hence you can see some based woods, and other odd trees free standing.
I think we do need to restrict it, its just I tend to fight a losing battle against people not wanting their precious marines splatted by demolisher or plasmacannon hits. Oddly the players who have models who would benefit the most from the cover in theory, eg guard, nids, orks, usually prefer less terrain so they can actually deploy their army!
The terrain deployment rules in 6th don't help. In the old system we used to have a neutral 3rd party deploy the table, or have one player set the table up, but the other pick the side. I actually think we should go back to the later.