Yes, most flex posts in the area are deployed in such a way that a bicycle can move into the auto lane trivially, and many of them I can actually slalom between. For a person on a bike, lanes that have this (Mass Ave as an example) aren't separated from the auto network in terms of navigation. There are some cycle tracks that behave somewhat like this, Beacon St in Somerville Northbound is the only one that is coming to mind locally.

Lanes like this don't behave like curb or greenery separated cycle tracks, nor like off street shared paths