I hate to bump an old thread, but this forum is so dead that I can probably offer the information you're looking for.
Tier I: IMER, IPN, SPR (formerly OPMA), UNAM, Canal 22
These are without a doubt the heavyweights of public broadcasting in Mexico.
IMER owns a boatload of Mexico City radio stations but the rest of its portfolio is really a hodgepodge—stations they received from other federal agencies, stations signed on in partnership with some states, etc. Thinking of IMER as the land of misfit toys in regards to its portfolio is pretty dead on.
IPN signed on the first public broadcaster in Latin America, and Canal Once is the largest public TV outlet by penetration. In fact in the 90s the IPN began building repeaters for Once TV/Canal Once to extend its network. (This led to some confusion in Tijuana when they built out channel 3 and flooded San Diego TVs with interference!)
SPR (formerly OPMA, "Mexican Public Broadcasting System") is another federal agency. It owns a network known as Una Voz con Todos (A Voice for All). Its transmitters (17 in operation, nine more to be built soon, a 27th possibly to be licensed after 2015) are real multiplexes: they carry Canal Once, Canal 22, their own network, an educational service, and UNAM's TV service. They've also jumpstarted national coverage of public broadcasters (which w
UNAM: Universidad Nacional Autónoma de México. Even I have trouble wrapping my head around the size and scope of UNAM. Has been dabbling in TV since 2000 or so, but its Mexico City station is low power and it owes almost all of its coverage to SPR transmitters.
Canal 22: Established 1993, formerly part of Imevisión in the 80s. When that was privatized a bunch of cultural actors got together and lobbied the government to set aside a station for cultural broadcasting. They did. Again, Canal 22 owes most of its national-level coverage to SPR.
Tier II: State networks, other universities, CDI
State networks are some of the most complicated operations in Mexico. They often are radio-TV operations with many transmitters (Sonora's Telemax has 59 of them, which is the highest) that are often at low power. Networks often don't get a lot of investment, either (some of them have budgets that would be in six figures in USD). They participate in program exchanges with the Tier I broadcasters which in turn extend their reach, through La Red México, A.C. They also produce and air local programs including newscasts.
There are also other university television and particularly radio stations. Universities are really active on radio, sometimes having entire networks of radio stations (such as the Universidad de Guadalajara), and some (including three in Durango, though not many nationally) have added TV to their scope.
CDI (Comisión Nacional para el Desarrollo de los Pueblos Indigenas): Broadcaster for indigenous areas, part of another federal agency. 20 AMs and 7 FMs with mostly local production, including programs not in Spanish.