What "switch" is it, that they are not flipping?
Depending on how they operate, there may be many different functions that have to take place....
Is their HD programming up full-time on that channel/subchannel (even if just upconverted)?
If not, then the encoders have to be reconfigured when changing from SD to HD, and also when switching from sending 3:4 to 16:9.
Bit rates may also need to be changed.
Do they multicast at all?
They might have to go into the encoders and turn off the additional channels, or reallocate bandwidth back to the HD?
Are they running the HD feed "live" (east coast time slot) rather than with the delayed (pacific time) feed?
There may be problems with tape machines, or the dreaded "delayed schedule 'cause the game/press conference/news bulletin ran long".
We sometimes have to join "Leno" in SD until the first commercial, due to having to record and rewind the HD tape feed, since we delay programming for our time zone. Maybe they do that?!
Do they have to get HD from a different satellite than regular programming?
They may not yet have an additional dish for HD. Perhaps they are still taking a news or syndicated program feed at the time the HD program starts, and the dish hasn't finished moving to the satellite where the HD feed is.
Or, maybe, the engineer (IF they even have one on duty) is distracted by some emergency and just can't make it back to "the switch" in time....most stations still consider the analog feed as the PRIORITY, so sometimes "stuff happens".
Many thing can be automated, depending on the specifics of the automation system equipment. Hopefully they are working on it...maybe it's budgeted for in the future?
Ken English, Sr. Engineer, KSL-TV/-DT.
"Not a REAL Engineer, but I play one in TV"