I'd been hearing rumors but, if Pitchfork is to be believed, it sounds like they might be true. They report:
"Now, if we were to tell you that the A.V. Club also reported that Johnny Marr, the former Smiths guitarist, has "been flying to Portland from Manchester to write songs" with Brock, well, that would be pretty orgasmic news for people who love Modest Mouse. And The Smiths.Read the rest HERE. Guess I might have to finally start paying attention to/listening to Modest Mouse. I'm a jerk like that.
Good thing it's true!
That's all we know about that right now, but hey, isn't that enough? Johnny Marr is working with Modest Mouse! Get excited!"