These events are prevalent during warmer weather months with an increase in tropospheric ducting whereby a distant SU attempts registration here the signal propagates via ducting to the distant site where its not authorized to do so in the zone controller. This can also occur when
the SU may be located at a point of higher elevation and whereby said signal propagates to the distant site operating on the same control channel frequency and NAC.
The later explanation may have some merit in that the SU's RID originates out of Grand Traverse County. But I don't think this is the case in that it's highly unlikely that this would be a coincidence of short spaced frequency reuse. It's far more probable the SU was roaming outside of it's
normally authorized area and simply tried to affiliate on a tower near you.
It's also a little bit of a mystery in that TG 4400 is not presently listed in the Radio Reference Database for the MPSCS. The only know facts
are the RID and that it was assigned out of Grand Traverse County.
I see this quite a bit in DMR Tier 3, specifically Capacity Max systems where the default System ID is 1. Part of Capacity Max systems is a Comprehensive Roaming algorithm where when the radio cannot connect to any known site, it scans the entire RF band and connects to any control channel with the same system ID. At this point, the radio gets rejected and continues scanning. TT