It's possible this can be successful but I think you're going to have to supply a bunch more documentation as part of that claim.

From Trip Delay: What Documents are required to evaluate my claim?

Quote:

Please note: If you opted to take an alternative means of covered transportation (such as bus, train, or taxi) instead of re-booking with the airline, you must provide documentation from the airline that verifies the date and time of the next available flight. This is to substantiate that the delay length meets the minimum length requirement as set in your Guide to Benefits.

For a normal trip delay claim you would "only" need to show that your flight was rescheduled to arrive beyond the 6/12 hour delay window. With a cancelled flight now you need to somehow come up with written documentation that the airline wouldn't book or interline you on another flight within the delay coverage window.