Reading the comments on Munro, I am now thinking that the best option is an extension of the subway to Steeles combined with LRT north, all the the way to Elgin Mills. If it is demonstrated that the maximum passenger carrying capacity of the LRT line will be enough to meet demand for some time to come it would provide a transit option for the greatest number of people in the shortest amount of time.
York Region takes greater control over the project and it's timeline, the fight between the disparate municipal governments working at cross purposes , each in the best interests of their citizenry, comes to an end and we don't have to wait until the DRL is built to begin providing transit to residents of York Region.
An easy underground transfer from LRT to the subway will cost mere minutes in time. Diverting more passengers to the Spadina line through route detours, reduced fares on the Richmond Hill go line to encourage greater use and integrated fare systems could further help alleviate crowding on the Yonge line.
Start digging the subway to Steeles as soon as the boring machines are available. The environmental assessment is complete and the need to get hundreds of buses daily off this section of Yonge is apparent. The effect on the downward sections of the line will be minimal since the bulk of the commuters boarding at Finch will simply move north to Steeles. The LRT would provide a fast, reliable option for commuters heading into North York or Mid Town while those traveling into the core would more likely choose the Go option due to a single mode down to their destination.
York Region is the fastest growing in the GTA and Markham, Vaughan and Richmond Hill all have solid growth plans that include urban density throughout the Yonge Street Corridor. This is a goal that should be supported but the bickering over which transit opportunity should have priority only serves to stagnate the disirable development.