I've never tried to set my Ruby up as a TT bike, though I guess it could be done. A bunch of factors made me get separate bikes. I've got the Ruby pro, which has carbon bars, so clip on's are not an option. I also got a screaming deal on a used TT specific bike and it was just a given that in my size it would have 650 wheels. For stage races (which I do probably 4 to 5 of a year) it is sooooo nice to not have to touch my road bike between the TT and road race/crit stages. Changing saddle positions, fussing with handlebars is just something I don't really need to have to think about.
A few plusses about the system are that I still get to ride my 700's for road races - if you have anything non-standard you can forget about getting any neutral support. For TT's support doesn't really matter so much. I was also able to get really good prices on a deep section front and rear disc wheels, as many taller triathletes are switching back to 700c gear and selling off their 650 stuff cheap.(I got my Hed disc for $260! with a cassette)