Tandems in Everest challenge go off in the first wave, which iirc is with the Cat4's.

Presumably they start the tandems early to give the most time before the time cutoff.

The commotion Classic was run on the same course as a Crit for singles with the tandem race earlier the same day.

Obviously a crit has to be run seperately.

An endurance race like EC I don't think it matters mixing tandems in a mass start be cause things sort out anyway by climbing speed.

More typical RR, I think you'd want to run separately, but you could just stagger the start time a few minutes, just as they do with different Cats