It's not the bike brand that is the issue, it is the brand of motor.
Bosch, Shimano, and maybe Yamaha are the big boys on the block and even though Bosch has changed their motor mounts and battery sizes, the old versions are still available. A friend just had his Gen 2 motor (circa 2015) replaced with an original Bosch.
When a bike manufacturer produces a bike with one of these motors, they have strict guidelines, For this, anyone who is authorized for these motors can repair regardless of bike brand.