Yeah, they are removable. Both Maisto and Bburago. With Bburago the rims are placed "in" the brace discs, who are clicked onto the pins. Maistos have the wheels "shoved" onto small cylindres who are clicked onto pins. Kinda like Bburago. But you can't combine Bburago wheels with Maisto models or the other way.
Good luck with your customising job(s) and I hope you will post some pics here!