My reading of it is as thus:
The cost includes a hardware piece that attaches to your commlink/deck/RCC enabling it to act as a sort of Super Master. It can (in addition to its normal duties) create a TAC network with Rating x 1.5 devices (which need no additional hardware), which in turn can also be masters of a PAN. The TAC master's Firewall Rating is shared with the other members of the TAC and the members of their PANs. Apparently you can (depending on the Pi-Tac) assign half/all of the Pi-Tac DR to the Firewall and/or DP, in which case I'd assume that the DP boost only applies to the master. But I can see how one could interpret that the Firewall bonus only applies to the master device as well.
The reason why I interpret it this way is that if you were limited to 1.5xPi-Tac DR team members and each device had to be a slave on the master device's PAN, you could have no more than DRx3 devices total. Since the highest DR of any commlink/deck is 7, that means 21 devices shared among 8 team members for a Pi-Tac III, that's less than 3 devices per team member, which would hardly cover the biomonitor, one weapon, and one sensor (for the audio video feeds). Any paramilitary unit is likely to have multiple weapons per team member, a biomonitor, and multiple other devices providing sensor feeds (cyber-eyes or glasses/goggles/contacts, cyber-ears or earbuds, and so on), not to mention drones and each team member's communication device. This makes placing an entire squad's worth of gear under a single device impossible.
ETA: Each "team member" is a persona, so the the slaves to the Pi-Tac device will be drones/vehicles or commlinks/decks/RCCs. In most cases, the drones/vehicles should probably be a device under another team member to more efficiently use the slots, but if needed, any persona should be able to act as a team member. Technomancers could also be a team member (but not the master) depending on whether you rule that the member devices must run software or simply need Matrix connectivity to take part.