Haha, yeah we have had a few off-topic discussions, and I think the naming thing is a relatively minor detail. On the last page I posted my alternative to the CityRail concept, which includes a greater distinction of what type of rail service is actually included on each corridor (
http://www2.andrew.thejohnsonclan.ca/GO_REX_v2.jpg for those who missed it).
Doing discussions about Regional Rail I think are a lot different than local transit, because RR is pretty much confined to where the rail corridors already are, so there aren't any discussions about alignment (like there are with the DRL). The discussions mainly centre around what type of service for what corridor, how far out should that type of service extend, etc.
Realistically speaking, the only corridors that are capable of hosting REX at this point are the Lakeshore and Georgetown corridors.
The Stouffville corridor can be upgraded to REX-capable, but that would require grade-separations and double tracking (not exactly cheap, but doable). Same goes with the Barrie corridor, but to be honest I can't really see the demand being there for a full REX service.
The Richmond Hill corridor would need some pretty significant upgrading and realignment in order to be REX-capable. That whole section through the Don Valley is neither accessible nor very direct, and the connection possibilities with existing and planned rapid transit lines suck. With the current alignment, you hit Sheppard and that's about it. My map reroutes the line around the west side of Don Mills, for a better connection at Eglinton.
The Milton corridor is the hardest one to pinpoint, because so much of the available service level depends on freight. Any significant increase in GO service on the Milton corridor needs to be accompanied by the construction of a freight bypass between Bramlea and Lisgar. Without that, there would need to be at least 2 more tracks added into an already crammed corridor, which would be enormously expensive. IMO, diverting freight traffic off that line, even if Metrolinx has to pay to build a new line on which GO trains will never run, is a worthwhile expense compared to the alternatives.
Same thing goes for the Midtown line, because the Midtown and Milton lines are the same CP mainline. Build the freight bypass and convince CN and CP to share the York Sub (even if it means Metrolinx paying to add an extra track to that line), and you get both the Milton and Midtown lines available for GO service.
If that's the case, both of those lines would be REX-worthy. But as it stands now (and that's why my map shows what it shows), 1hr or 30 min diesel service is about all that's possible right now.