When you have more than one tivo, the other unit(s) show up at the bottom of your list of shows... Just click it, and the other units 'now playing' pops up, and then just hit play on your show to view it. Trick play, as in Ff, rew, 30 second skip, etc function as slickly as when viewing off the 'local' box. Also depending on your cable providers use of the 'copy bit', you can copy shows from one tivo to the other vs just a streaming play. Some companies don't use the copy bit, some use it just on premium channels, some could even use it on all channels. I happen to know comcast well, and they generally only block the premium channels: hbo, etc from being copied.
When on a mini, the 'now playing' list is the one from the box it is paired with, and it works the same way.... Just click the other full blown tivo in the list to view its shows.
It will not "automatically" go to live tv, as they borrow one of the tuners dynamically from the host/paired dvr, and after a specific time-out, the tuner is released back to the host tivo. It IS just one button press on the remote to access live tv.
-Roamio Pro/Slide Pro
-Stream (Gotta go unplug the sucker one of these days!)