Because of the mess at Kipling as well going into Halton, Metrolinx wants a BRT on Dundas Only to keep it one line requiring no changes along it.
An LRT on Dundas is only good between Cloverdale and Hurontario to deal with the issue at Kipling, But there is no plans for Cloverdale in the 25 year plan at this time that includes extending the subway there.
Hurontario & Main were Hwy 10 at One Time and is under Peel control now.
Based on density on Dundas west of Hurontario to Burlington, Going to be hard supporting a BRT in Halton, let alone an LRT. Even Mississauga is hard press supporting an BRT west of Hurontario and more so west of Erindale Station Rd.
The EA for Dundas is to get underway in 2016 and that may change on the revise Big Move Plan due in 2016.
Theoretically the corridor between Hurontario and Kipling could be built to support both LRT and BRT vehicles, much like what Ottawa was proposing in the old N-S LRT plan that was cancelled in 2008. The plan was to have the Transitway lanes downtown upgraded to include LRT tracks, and to run the N-S LRT and E-W Transitway routes in the same lanes.
Both vehicle types would be low floor, so there wouldn't be an issue with platform heights. It would be a relatively rare instance of doubling up two different technology types in the same corridor, but it's not like it's impossible. If you wanted to you could even build the corridor in such a way that the LRT stops at all stations, while the BRT runs express or semi-express all the way to Kipling, to avoid a duplication in service.