It would take additional hardware as well as a firmware upgrade. It's very unlikely Whistler will do this, given that they now have several other Phase 2 capable scanners already out there. It's an old design, as well, actually based off GRE's PSR-600
Whistler models that can handle Phase 2 include the WS1080, WS1088, WS1095, WS1098, TRX-1 and TRX-2. See our wiki for information on each of these scanners...
Whistler Scanners - The RadioReference Wiki
Mike