Before Nextel was what it is today (a combination of nationwide push-to-talk and cellular phone), Nextel was a series of LTR trunked systems that were available for lease for local area communications, very similar to community repeaters. It was popular among business such as taxi services, towing, delivery, agriculture, etc. Subscribers would be issues a radio PTT ID for their portable or mobile radio, and assigned to a subfleet.
Some of these systems still exist, but have mostly been phased out in lieu of what Nextel has become today.
The old generation of Nextel systems were monitor-able with a scanner, but modern Nextel is based around IDEN TDMA technology, which is not monitor-able, and if it were, would be illegal to monitor because of FCC rules governing eavesdropping on cellular phone systems.