Tivo Mini tuner sharing ("piggybacking")

I've just received my Roamio Plus and 3 Mini's the other day and am still working through the setup. I'm coming from a Windows Media Center setup with 4 extenders spread throughout the house. I'm comparing features and noticed that tuner allocated to the mini won't "share" with the main Roamio while it's being viewed in another room.

For instance, Roamio Plus is recording 4 shows and viewing live channel ABC. If I tune to ABC on the mini it takes the 6th tuner to do this rather than...

Tivo Mini tuner sharing ("piggybacking")

Tivo Mini tuner sharing ("piggybacking")