FYI
Below is a link to a ARRL lunch discussion with the FCC held on Jan 25, 2024. At 1:12:45 the question about linking GMRS repeaters is asked. The response is no and they cite 95.1749 and 95.349 - they said that telephone and "public switched network" includes any kind of network. The exception is to control the repeater, i.e., turn off or on.
I was told by a third party that some repeater owners in PA have been warned fairly recently but I don't know who.
Here's the link to the video of the luncheon
§ 95.1749 GMRS network connection.
Operation of a GMRS station with a telephone connection is prohibited, as in § 95.349. GMRS repeater, base and fixed stations, however, may be connected to the public switched network or other networks for the sole purpose of operation by remote control pursuant to § 95.1745.
§ 95.349 Network connection.
Operation of Personal Radio Services stations connected with the public switched network is prohibited, unless otherwise allowed for a particular Personal Radio Service by rules in the subpart governing that specific service. See e.g., §§ 95.949 and 95.2749.