Fowler has higher potential than Dobes or Montembeault but even he is not what I would consider a "blue chip goaltender prospect" at this point.
Fowler has some very good tools as a goalie and HAS played amazingly well for BC, and to start his AHL career. But I don't think Fowler has proven enough yet against pros to have the kind of value that a top goalie prospect can have.
If we see Fowler continue to thrive next year in the AHL throughout the season and in the playoffs, then Fowler will begin to make more of a case for himself to be held in the same kind of regard as guys like Askarov or Cossa, and Wolf before he firmly established himself in Calgary this season.
But right now Fowler is still largely unproven against pros, and needs the reps to "show his stuff" and establish himself before teams will be ready to give back good value in a trade for him.
It just is the reality of the position of goalie. The top guys and blue-chip prospects have incredibly-high value but aren't getting traded anytime soon, and the more "middling" prospects don't have much value overall.
Fowler is a good prospect and has value right now. But given that he is still unproven, he would only be a secondary, or even tertiary add to a package for a 2C.
And that would be no-bueno on the Canadiens' part considering Fowler is the best goalie prospect in the pipeline.
It is what it is.