Under 'prohibited communications' in the Part 95 rules, find:
(12) Messages which are both conveyed by a wireline control link and
transmitted by a GMRS station;
Thus, no station audio can come via any wireline link. Note this doesn't specify the PTSN, it's any wireline link.
Boy, talk about taking the rules out of context to suit your purpose. What you are referring to, Section 95.183 "Prohibited Communications", subsection (a), paragragh (12) refers to what a person (station operator) cannot communicate, meaning that if it has already been sent through a wireline control link to a GMRS transmitter, it cannot be relayed further by another operator. A simple overview of the other 12 items on the list make it obvious it has to do with what a person can or cannot SAY over a GMRS system.
The way you're interpreting the rule, it completely contradicts Section 95.127, "Controlling a station from a remote point", as well as section 95.141 "Interconnection Prohibited", which states that "No station in a GMRS system may be interconnected to the public switched telephone network
except as and in accordance with the requirements and restrictions applied to a wireline control link (see § 95.127)." (emphasis added by me)
Section 127, subparagraph (e) states: "(e) Any device used to establish a wireline control link which is attached to the public switched telephone network after April 1, 1976 must be registered with the FCC and must comply with the standards incorporated in a registration program to protect the public switched telephone network from harm (see part 68 of the FCC Rules)."
So section 127 states that as long as you are using Part 68 compliant equipment, a GMRS station may be connected to the public switched telephone network, which completely nullifies the argument in this thread. It
IS allowed through direct connection, DSL, dial up, dedicated phone lines, cable modem, or GMRS link.