Rick,
I have a lot of clients where MQ, and other middleware, support is split by platforms. While this may may make sense based upon skill sets (especially on z/OS), I'm not generally in favor of this kind of split. There definitely is platform engineering knowledge that is essential, particularly on z/OS, but most of the MQ skills are cross platform. I prefer the middleware teams to have a more holistic point of view, with one team covering all platforms, data centers, and lines of business. You can then augment that with the necessary platform skills. Unfortunately, this is the pattern that I see the least frequently.
I also frequently see splits by either Line of Business or by geography. Most of these types of splits are based upon organizational convenience rather than from functional necessity. I also see splits between Application Developers, Architects, and Administrators. This also tends to blur the lines of responsibility.
I would prefer to see a single group, delivering MQ as their product, and entirely responsible for the successfully delivery and use of their product within the organization. Combining responsibility with authority is a constant organizational challenge, as it leaves nowhere to hide. The typical organizational behavior is to obfuscate responsibility as this also defuses blame and so lowers risk for the individuals involved
Regards,
Glen Brumbaugh