No, nothing wong with maya... how do you know they arent trimmed?
First maya is a surface modeller so theres absolutely NO nurbs solids defined in maya. Also theres no solid info in IGES, but proe will automaticaly attempt to make all iges import solid shells later on in the process (theres a reason for prees high price tag!). So it is expected that you will get a load of nurbs patches that represent your surface (thats whayt proe does internaly too it just stitches them together for you to se as ONE solid internaly ist still those surfaces, also if you just export a well done patch modell form maya youll get one solid in proe!).
Anyway its most likely thet the proe modell is HUGE compared to maya scene size. so if you hit a to fit everything yodu be staring a t a blank screen. try adjusting you near and far clip planes to suite.
you can use viewClipPlane -acp; and it will fix the active camera (for that view only so you may wish to manualy st the close closer and far further).
Anyway you should use the step importter its far better than the iges one. just import the dirrect connect plug and its there
Now after this you will START to have porblems.
Fistoff maya will not tessalate over shells, and secondly your defined surface is much a jumble of stuff on screen. Amd im a afraid deforming this object is ABSOLUTELY out of question (if you need it to deform export stl and mege points). Handling iit as solids is easy tough.
Now the tesselation can be fixed in 1 of 2 ways, sufficently high edge tess. Or micropoly one. Idf prefeer the second allternative but sadly thet means no maya inetranal renderer renders.
Now youll prbably get deecentreuslts tough one thing mill be of problem, angular precicion might cause havoc. NOW it need sto be sufficently high (in both proe and maya) or radial arrays will blow appart. problem with this is that the setting should be set before you start modelling in proe! Step handles this a bit better tough. Still the precicion might be the problem. NAd the etsselation of Mr leaves much to be desireed if comparerd to the way prman works.
once you get this far youll may have even more problems on your hands! So you se importting/ exportting is NOT simple especialy between two sodfts of differing pareadigms.