There's a sign further back on Rue du Pont Champlain indicating that no bikes are allowed. I've only travelled this area by bike, so I've only seen the first "no bike" sign and then turned back. I'm not sure what the status of the bus road is, but I'll try to take a look at it the next time I ride down Bldv de Ile des Soeurs

Hey! Yes, I tried biking on this the other day. There's a no bike sign, and it just leads to a highway on ramp