But will more frequent trains attract enough ridership to fill them up with passengers?
We will get a final report soon which should answer this question.
However [this is speculation], since preliminary staff reports noted that 15 minute frequencies would not pull enough people away from Bloor/Yonge to defer the DRL, and the "fix" staff present is 5 minute frequencies through the central portion, I suspect that the model finds that ridership of this new service will be high enough (with suitable fare and bus connections) to have a noticeable impact on the passenger count transferring at Bloor/Yonge.
There's no obvious reason to expect Smart Track to Kennedy wouldn't achieve 25% of the ridership that DRL @ Sheppard might. While ~4500 peak hour load isn't huge, it's also very cheap (~$1B over $RER for Union to Kennedy?) giving it a way better ridership/capital ratio. 4500 is about 15% of the upgraded Yonge capacity south of Bloor, so it's not a trivial amount. If nothing else, it gives flexibility when Yonge gets unexpectedly shutdown.
The western portion removing significant ridership from Yonge south of Bloor isn't as likely but I suppose a few hundred counts and that stretch under University has capacity struggles of it's own.
Even seems cheaper than Yonge upgrade costs (ATO, redoing termination stations [unfunded], extra trains, etc. to achieve 10% boost in capacity).
The DRL will still be required in some form at some date. Heck, even if the DRL was built a DRL2 will still be required in some form at some date
The article says operating expenses are still to be worked out. I doubt each portion (east/west) will be much higher than the Spadina extension per km. So maybe up to $80M/year in subsidies to operate the plan (heavy rail and ECLRT extension).
The Union to Yonge Line transfer will be a bigger issue. It takes me 3 minutes to make that walk in rush hour, and I'm a fast paced walker. Could be closer to 5 minute for people to make that walk including wait times for Yonge Line train.
This can of course be fixed in future if a large number of people transfer (moving walkways within Union or even tunnelling some RER services downtown away from Union). In the short-term, I suspect most people taking it will have a destination within 500m of Union and will opt to walk that last portion without a transfer to Yonge line. Those going to destinations closer to Dundas (Ryerson/Eaton Center) will probably continue using Danforth.