To clarify, the Unication G4 and G5 (and presumably the upcoming G2 and G3) will decode QCII tones over P25 conventional or trunking (FDMA or TDMA). There is no special signaling involved, no control channel data (other than the voice channel grant), and dedicated individual talkgroups are no longer required. They function the same way a Motorola APX would with QA09000 Digital Tone Signaling, by decoding the tone frequencies themselves as an analog radio would.
From the Motorola APX Radio Software catalog:
DIGITAL TONE SIGNALING
Reduces response time by alerting entire groups of responders
simultaneously. Commonly used in Fire Rescue to alert first responders
to an incident by broadcasting a series of distinct, recognizable
tones followed by a voice transmission from dispatch. This allows an
entire fire department to be simultaneously alerted to an emergency
situation, as opposed to unit-to-unit dispatch (Call Alert). Responders
can keep their radios in a quiet or silent mode until an alarm is raised.
This feature works on P25 conventional or trunked systems, providing
digital Quik-Call II operation (identical in operation to the legacy analog
version). The feature supports encode from an APX portable or mobile
with a DTMF keypad from release 7.17.5.
From the Motorola APX Radio Software catalog:
DIGITAL TONE SIGNALING
Reduces response time by alerting entire groups of responders
simultaneously. Commonly used in Fire Rescue to alert first responders
to an incident by broadcasting a series of distinct, recognizable
tones followed by a voice transmission from dispatch. This allows an
entire fire department to be simultaneously alerted to an emergency
situation, as opposed to unit-to-unit dispatch (Call Alert). Responders
can keep their radios in a quiet or silent mode until an alarm is raised.
This feature works on P25 conventional or trunked systems, providing
digital Quik-Call II operation (identical in operation to the legacy analog
version). The feature supports encode from an APX portable or mobile
with a DTMF keypad from release 7.17.5.