Think I found it. If I option-click near the top of the track header, it selects all the regions in the track, as you described. If I option-click near the bottom of the track heard, it makes an exact copy of the track, regions and all, the only duplicated track has everything selected. Do you get the same behavior?

Interesting! No, I get the same behavior (no duplication) no matter where I click in the header, with the relevant Preferences either on or off, at any zoom level (track height/width). I wonder if that's an actual feature rather than a version- or system-specific anomaly..? Perhaps it could have something to do with the particular Track Header Components options enabled (via right-click on any track header).. Anyway, I'm glad you found a solution, even if it is mysterious and unexplained.. ;-)

In my case ⇧⌘T does the trick and moves the region to any selected track. (LPX 10.4.8)

Hmm, here in Logic 5.0 Shift-Control-T still works as described earlier in the thread -- Shift-Command-T seems to Hide/Show the Global Tempo Track. But then again I probably didn't switch to the latest (frequently changing) Key Command defaults when upgrading, so I wouldn't be surprised to find that different shortcuts may be in effect.. :-)