Prepping spots for delivery to a TV station was the topic of a recent thread on the AE-List. Paraphrasing, it was noted that while BetaSP is disappearing from post houses, many TV stations and cable operators still require BetaSP, or DVCpro. Many are also using services like DG FastChannel, and the networks and major cable channels are also taking Digibeta. Few are taking digital files, but in any case it's best to check early for specific delivery requirements.
Capria.TV notes that "though most video pros don’t deliver PBS programs to the network on a regular basis, the PBS spec is commonly used as a benchmark throughout the industry." Frank adds links to PBS Red Book guidelines and definitions in his post New PBS Tech Specs.