I have done 2 SS1600Ks in Ontario/Quebec. Both rides were done on my 1992 Yamaha FJ1200. Cannot comment on your proposed Quebec route.....but it looks like fun. Interested in hearing responses from people from that area.
My first ride I went from Kincardine, Ont down to London, Ont on secondary roads. Then road the 401 to 403 through Hamilton and up to the 407 and back to the 401 all the way to Montreal, Quebec. From Montreal I went up to Ottawa and then took secondary highways all the way home through Alqonquin Park. The ride took me 18 hrs and 27 min with an average speed of 90.2 km/hr (54 mph). 6 gas stops and 1 stop for a break.
My second SS was completely in Ontario and was mainly all secondary roads. The route took me from Kincardine, to Orillia and then north to North Bay on Hwy 11. From there I continued north to New Liskeard and on to Cochrane. From Cochrane I headed West and then back south on 655 and then 144 to Sudbury and back home. The ride took 19 hrs and 36 mins with an average speed of 86.7 km/hr (52 mph). 8 gas stops and 4 brief rest stops. Moving average speed was 93 km/hr. On this ride I ended up sitting for 40+ minutes on Hwy 69 due to an accident. I also hit some significant construction on 655 where I recall one of those "pucker" moments when with very little warning I went over the crest of the hill on the highway and the road switched to a loose wet mucky gravel mix.... I ended up riding about 25 kms in that mess.
For both rides, I doubt I could significantly improve my overall average of around 90 km/hr (54mph). Therefore, although SS1600K is very doable, a BBG (1500 miles in less than 24 hrs) would take about 27.5 hrs. The only way I believe a BBG is possibly in Ontario is to start in Windsor and ride the 401 freeway for 750miles and then turn around and go back on the same highway and hope for no traffic in Toronto/Montreal (very unrealistic).