Video shot at 30p is no different to Vegas to video shot at 60i.
Only issue might be FXs, they'll most likely be applied at 60i, don't think you'll notice the difference though, but the camera footage will still be 30p, in fact there's no way you can make 30p into 60i.
No matter if you shoot 30p or 60i the camera still records 60 fields per second. The difference is that at 30p the two fields are taken at the same point in time hence the difference in temporal resolution.