No doubt that a fly like this would probably be a good trout fly as well - the large head and whiskers would indeed be a "pusher" and attractant for big browns at night. As Sal notes, the profile would likely be suggestive of a sculpin, which is, of course, similar. In essence, a pattern with these characteristics is similar to the large trout streamers with bulky, wool heads popularized by Kelly Galloup and similar designs.
Madtoms are typically found up WW streams to where they start to transition to trout water - think the lower ends of a larger trout stream that gets warm in summer and where one would expect to get a big brown at night. Trout in those areas would likely key on a stonecat. Up in colder water, like the CV limestoners, madtoms are rare or non-existent.
Overall, stonecats are prey for bass and WW species, but a fly tied with these characteristics would be a good trout streamer. Personally, I like my trout streamers to have a hook much further back in the fly to get good hook-ups. For bass, a fly with a hook in the forward third of the body sticks well...but would probably miss some trout, especially smaller ones.
