You shouldn't normally have SRS wiring cut by seat tracks but if that's the case, even SRS wires can be repaired according to Volvo now so you're being hosed by someone. Tell them to just repair the wiring. If it's still under warranty, its repair or replacement would be covered unless they could somehow legally prove that you personally and intentionally tryed to damage those wires, not too likely IMHO.
Worst case: If it's out of warranty and after they try to repair the wires, there's then too much resistance in the repaired circuit (not likely), it'll set a code and your SRS system will still be inop.