Limitation that i have seen in Moi is the number of surfaces with the Max SUbdiv plugin!
(8 000 seems the maximum) Very Speed! less than 3 minutes!

Maybe they have more strong one by their side!
Objective was to send them a nurbs file with edges welded! (not subdivided) :)

File Step was something like 420 megas, a file 3dm 290 megas : with 50 000 faces welded! :)