It's easier if you stop thinking of MSP, Logan, Cambridge, as separate systems. They are sites sites or maybe "nodes" on what Bill is accurately calling the Commonwealth trunk system. Even if that's not it's official name.
All of these sites as well as the Zone 1 Boston/State site and the 700 Mhz overlay use the same Motorola controller. They are all interlinked to some level.
TG 69 is a MSP digital talk group used on the Logan system. If they go out of that area and into one that is analog, the radio will revert to analog.
Back some years ago Boston changed all of their talk groups to eliminate any duplicates so that the Zone 1 and then existing City of Boston trunk system could be merged. Since then, all talk groups are coordinated so that there are no conflicts.
That's on the Massport system. Is that the same talk group for zone 3 on MSP? I know massport has its own system separate from Msp