Hello folks, thanks for the prompt replies! As @scook suggested, changing the file extension back to .cwb worked perfectly, and SONAR opens it perfectly. Thanks so much!
As a side note, I am obviously a completely new poster here, and I am thus unaware of any cringe-worthiness of the Cakewalk bundles as your forum mythos or etiquette. FWIW, I have been using SONAR since 2004 (starting with version 2.2) and currently run SONAR PRO (have not upgraded to Bandlab, sorry [not sorry]). I've always felt Bundle files were absolutely fine for archival purposes as well as a mental signifier that says "OK, this track is complete. I can be done now." Project files are for something you are currently working on. Knowwhatimean? This has been the only problem I've had with a bundle, aside from a damaged CD-R that made the bundle data file corrupted.
To each their own, I suppose. Regardless, thanks. Someone needs to tell Google Drive to get their sh!t together!