Alas, I haven't worked with transport objects that often but to my knowledge they're tied to Live's master transport all the time. See the testcase here:
I use this in a normal Liveset (so 120bpm, 4/4 signature). When trying to change the signature you'll trigger an error. And even though I set the transport to 160bpm you'll notice that it still follows Live no matter what (bang it, check the output).
As such my conclusion.
You'll also notice that by using a live.toggle (or Max toggle) you can't start/stop the transport as would normally be the case.
also; don't be fooled by the helppatch. The moment you open the helppatch for transport while in M4L edit mode (or if you simply have a Max license as well) then at that moment the transport won't utilize the Live environment but that of Max. So; opening the help patch would suggest that transport can control metro, while within Live metro will only listen to Live's global transport.
Just my general theory combined with a little experience. As said; I haven't messed with transport all that often.