Many professional and semi-professional rally drivers tend to hire cars for the whole season nowadays from specialised garages.
Its much "cheaper" than owning one and allows you to race with top quality gear. With a specialised garage and mechanic to send the car back to for rebuilding etc.
A bit like a lease. The car doesn't belong to them but to another company and depending where/who they rent them for the ownership may define the number plate. Its an all in service.
Where I live the rental companies have caught onto this and all their cars are now registered in a little village way up in the Swiss Alps where tax is cheaper even though they never saw the place! They save thousands.