When I got my cl-65 type back in '97, I asked about the 604 type. The guys in CYUL told me that while the planes were quite similar, it was a separate type rating. At the time they did not have a short course to get the additional type.

So, unless I am out of date with this info, they are not interchangeable. It is a shame, this would open up a lot of possibilities for quite a lot of drivers.