I would probably make the T2 the master, because the E80 won't send ANY CC00/32/PC# to external gear from the Keyboard Parts without an incredibly convoluted workaround (we are STILL waiting for Roland to address this
).
By this, I mean, it WILL send the codes for it's own internal voices, but if you have an external keyboard that needs codes that aren't already part of the E80's ROM, you have to use the workaround.
AFAIK, the T2 doesn't suffer from this.
But getting the T2 to trigger arranger actions (Variation and Fill changes, ARR on/offs, etc.) might be a LOT harder (in BOTH directions, to tell the truth), so I would recommend an FC-7 pedal to control the E80's arranger, while you trigger it from the T2's keyboard.
I hope this helps.