You can hear any TG, *as long as* a user on the site is listening to the TG in question (their radio tells the system they want to use TGID "x" and the system begins to transmit that TGID) or the site has been programmed to retransmit that TG all the time.
I'm not sure just why they would do the second, unless maybe the Moto rigs don't actually "register" a TGID when scanning? But for example here in OKC I can always hear Troop G (Lawton) even though they rarely get closer than Chickasha.
The first happens quite a bit. I occasionally hear a TPD TG, frequently can hear ambulance services from the Lawton area when one of their trucks are transporting to the metro, things like that.