That was a pretty easy fix. My Xbox 360 license transfer issues have been resolved, and it legitimately took nothing more than a simple phone call.
I received a follow-up voice message two days later, as promised, letting me know that the license transfer was still being worked on, but it would be resolved soon and to give them a call back if I had any questions. Later on that day, I received an e-mail letting me know that the transfer was complete. To fully resolve the outstanding issue, however, I would have to go through a manual re-downloading process of each and every individual item purchased while the hard drive was being used on the previous hardware. It was an easy process, if not time consuming. Your “Download History” in “Account Management” is painless to go through, so I sat with a drink and went through one-by-one re-“downloading” each item. I place “downloading” in quotes because the download immediately jumps from 0% or 1% all the way up to 100%, since it is only updating the license on the downloaded content, rather than fully re-acquiring said content.
After going through this process, all Rock Band DLC was accessible even when the ethernet cable was unplugged. Good job, Microsoft.
Now if only we didn’t have this pesky problem called “DRM” that made it impossible to use the things you thought you paid for but really only paid for a license to use at the sole discretion of the overlord company…