There are specific routes, but they can, and do, change. I've stayed at POP 5 times, using DME each trip. Four out of the five times, POP was the first stop, but one time it was the last of three stops. The bus went to CSR, AKL and then to POP.
When I have stayed at BW, the bus has 'normally' gone to YC, BC, BW, CBR. But the last time, we went to POR first, then to BW....so yes, the routes can change.
But, it isn't a case where the value resorts are all clumped together.