I've only got one BLI loco but I've not yet put RailPro into it. Undecided if I'll do this and use it as a "test bed" or maybe get rid of it (Hey BLI, when I pay your high prices I expect something that's accurate, not a close enough is good enough repaint!).
With that rant over, I don't know if the T-1 came as non Paragon or not but if it's a Paragon series I imagine it'll be a complete rewire like my BLI will have to be; all the different wires to the bogies, motor, lights etc are all terminated in small JST style plugs that plug into the BLI DCC board. These plugs are smaller than the standard DCC size JST plug.
I'd really hate to discourage anyone from RailPro because RP is good but I'm not sure a BLI (Paragon at least) would be a good first time install for anyone, especially if they're thinking of possibly reverting it back in the future.
- Tim