I think it's all part of the new transport interchange, which going by plans for trasport interchanges in other parts of the country will include things not at all related to transport at all, such as supermarkets. The old bus/mulitstorey car park has been demolished, presumably these will also be replaced in the process.
Yeah, we have one of those 'transport interchanges' which includes a large Tesco. Basically, Tesco funded a new bus station (after the old one had been closed down for about 6 years) to be built across the road from the train station (a small, unmanned station on the Stoke-Derby line) and also built thesupermarket and a large open-air car park. If it wasn't for the Tesco funding however, I doubt the new bus station would have even been considered.