Changing the timebase creates a copy of the original clip group. Both clip groups (the original and the copy) appear in the Clip List, but they have different timebases.
When dragging a clip group from a sample-based track to a tick-based track, the length of the clip group does not change. This is because clip groups are converted from samples to ticks after they are moved into tick-based tracks. The length of the clip group only changes with subsequent tempo changes. If appropriate, change the local tempo on the tick-based track to match the tempo of the sample-based clip group before moving a sample-based clip group to a tick-based track.
When dragging a clip group from a tick-based track to a sample-based track, the length of the clip group does not change unless it is moved to another time location with a different tempo. This is because clip groups are converted from ticks to samples after they are moved into the sample-based tracks.
Multitrack clip groups can include both sample-based and tick-based tracks. However, changing the tempo separates the clip group between sample-based tracks and tick-based tracks.