Well the problem is a culture clash, eingeering aps dont realy care what teh polycount is, they just do it. They dont manipulate the polys anyway. BUt as fate has it they dont export the real data all that well... why well they are closed sytems they vere never emant to do so. They try to tie you up into the sytrem.
Personaly autocad is probably the worst 3d program ever deviced, tough it core is okay. Alleway stry to get the paramatrics in, use iges or step or direct connection if you can. But bear in maind thes solid info is not exportted in way the t maya could use.