Anyway, to answer your question: Yes, I ordered it. It was delightful, if a little pricey at $8 a pop. (Oso Closo frontman Adrian Hulet may think it's "kind of sweet" that they charge extra money for the guacamole that comes in his band's burrito. But I, for one, do not.)
The promotion runs through March 12. At that point, you'll have to again relay to a member of the staff the ingredients you want in your burrito on command, per standard Chipotle protocol, rather than simply blurting out the name of a local band in an awkward--at best, let's face it--exchange.