You can test on site with a butt set and multimeter. Put meter across tip and ring, set to DC Volts. From that line, call someone then have them hang up on you, while you remain off-hook. You should see the meter momentarily (500ms +/-) drop to 0 volts. If you don't see the voltage drop, carrier is not providing a drop pulse/disconnect supervision/forward clear/whatever that carrier calls it. It's easy to prove one way or the other. Analog meter works best as it's easier to see the needle drop. Digital is fine if it's fast enough.
Cheers!