A1 (A1 R LE 01-15) - Regional Law Enforcement interop (all law enforcement GATRRS radios have this bank)
D1/D2 (D1 AT OP 01-15, D2 AT OP 17-31) - Travis County "operations" interop (all travis county radios-LE, PS, public works... have these banks)
E1 (E1 R PS 01-15) - Regional Public Safety interop (all public safety (LE+EMS+FD) GATRRS radios have this bank)
G1/G2 (G1 R OP 01-15, G2 R OP 17-31) - Regional Operations (all GATRRS radios have these banks)
"Regional" means GATRRS-wide
In case you were wondering where the other letters went:
B1 used to be county LE interops, no longer called this in Travis county; AFD/ATCEMS converted their B1s to Firecom 200/300/400s + Medcom 1-15
C1 is for county-wide public works interop
F1 is for regional public works
Other counties also have "B", "C" and "D" banks. B3/C3/D3 is Williamson County, B4/C4/D4 is Bastrop County, 5 is Caldwell County...
