Nope. Seen a number of Flexitys doing Woodbine and Kingston Rd trips during the day.When has this happened? I took the 504 up and down Kingston Road a few times last week, and it was always CLRVs. And all the 503/504B I saw on the tracker were CLRVs. All the 502s as well.
I wouldn't be surprised if one or two have slipped up there unplanned, but I don't think this is common or scheduled!
At 1.40 am you have 504, 504 (504 Cbr), 504 (504C) 504 (504Awl) cars out. 4450 (504C) is heading to Woodbine with car going to Dundas W and Dufferin Loop. 4181 is the lone CLRV out on the line. There is also 3 buses out for 504 as 504 (504Dbus)