I'm assuming you meant PeterGV's ScannerCast program. "Scan Cast" is the name of the streaming program contained within the Proscan software by Bob Aune. According to the to do list on PeterGV's web site, he does not indicate alpha tag support for older Uniden models like the BC780XLT. He does list the Home Patrol as the next model planned for support. See his lengthy to do list here:
K1PGV's ScannerCast To Do List
Proscan however does support alpha tags for your BC780XLT and you can stream the tags with either the full licensed product or separately with the free Radio Feed software that Bob recently put out. Go here for the details on both:
ProScan