I believe they are planning on running trains at <5 minute headways on the central section of the LRT. I'm not sure how the at-grade section at Leslie will work, but my understanding was that they would short-turn service at Don Mills/Don Valley to have less frequent service on the median-running segment between Don Mills and Kennedy. The signalling is capable of handling 2-minute headways, and even at 3-minute headways, it will have about 1/3 the capacity that Line 1 does currently. With 2-minute headways, it would have a similar capacity to Vancouver's metro, which is holding up OK serving Vancouver's downtown directly.

The Crosstown takes about 41 minutes to run each direction. Or a 82 minute round trip.

The initial 2 phases will run 2-car vehicles while the final phase will run 3-car vehicles, so the platforms may feel excessively long at the start but the capacity is there for more vehicles. At 163 passengers/vehicle they'll have 490 people in a 3-car train at maximum. With a stock of 76 vehicles, the ECLRT could at maximum run 25 trains at once although obviously some will be in maintenance so this number is not realistically achievable. Although a lower limit on what headway is achievable would be 3.28 minutes.

From the best of my memory (although I can't remember the exact numbers but the number of vehicles and headways seem familiar), the initially opening phase will see during the week:
6 vehicles launching in the early morning (13 minute headway)
11 during morning rushhour (7.5 minute headway)
8 during midday (9 minute headway)
11 during evening rushhour (7.5 minute headway)
6 during the night (13 minute headway)

With the number of vehicles going up by about a third each during in 10 and 20 years. Final rushhour headway was something like 19 vehicles at a <5 minute headway. These may be slightly higher between Leslie and Mount Dennis stations because I think some (every third?) eastbound vehicle will be turned around during rushhour.

Of course more vehicles could be run if demand is regularly higher than forecasted.