Leasing withdrawal with winter tires ?

Hello, I’ve had a very funny problem here, maybe someone has experience with it. The prehistory: In December 2007 I leased a V70 III to a local Volvo dealer for four years, a mileage leasing with 35,000 per year. In the binding order it has been noted that the vehicle is delivered with winter tyres. So I also received it. I bought the summer tyres incl. Felge from a friendly tyre dealer and the tires run down in four summers to the unusability. Currently, the vehicle is again on the original delivered winter tyre set, which according to tyre dealers can still be driven loosely two winters. Now to the problem: the local dealer is meanwhile insolvent and the leasing contract is traded by the Volvo branch Hanover, which will also handle the return of the vehicle. The precheck of the vehicle resulted in some shortcomings, over whose compensation has meanwhile also come to an agreement. But the statement of the branch, the vehicle must be returned by me with summer tyres, since the car returns to the factory.