It is used on many Shimano hubs but not all of them.
But yes, it could be used for a drive. Skarper is a company that uses Centerlock for its left hand side drive:
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Elegant idea, but it looks like the engineering got complicated real fast.
I guess you can not use a belt directly on those spline teeth, due to the force (=shear force on the belt teeth) required at that small radius to get reasonable O(50Nm) torque across. So they decided to build a geared drive into their replacement disk rotor, instead of going with a lightweight rotor large enough to be driven by a belt a la Aram's BikeOn solution. Which means in principle they could have kept the motor/gear unit quite compact, albeit heavy, but then they decided to put the battery into the same enclosure. Well, there goes the elegant solution out the window....
I understand why they want to keep the original brake caliper (so nobody has to mess around with reconnecting the hydraulic line), but the way they do it makes the rotor complicated: the inner part rotates driving the hub, the middle ring is stationary, and the outer ring serving as the brake rotor has to rotate again.
So, as far as removable drives go, there are two brake rotor replacement solutions, Bimotal, who are selling ($2k), and Skarper, still in preorder and aiming at $1800, and one cassette adapter solution, Bikeon, selling at $1250.
Not an upgrade solution for an existing bike, Fazua (sounds Chinese, but actually Bavarian for 'get going already, dammit!') had a removable motor/battery solution, but it needs a manufacturer-integrated bottom bracket bevel gear, and in the latest iteration they gave up on making the motor removable. (My guess is because they did increase the torque, and felt secondary/reaction moments would be too difficult to control. Online some people complain about motor screws working themselves loose even with the bolted solution.)