22 - 23 km/h on the roads on my mountain bike - not on trails. On trails I don't keep track of average speed - it all depends on the trail.
As well, the trails are a bit hidden. You need to talk to someone (like me) who knows about the milne trails. For example, the one right next to the conservation area starts off of princess street (off 48) and ends in Camp Chimo (off mccowan). Trail is maybe 2.5 km long. Not worth a long ride to come out to, but if you live in the area, you might want to check it out.