I never did receive a solution.
Making a copy of a file and XREFing the new file defeats the whole purpose of an XREF. The goal is to minimize repetition and error with XREFs.
The only insight I can offer is what I ended up doing. I was working on a single family subdivision at the time. We needed both standard orientation and reverse plans. I made an XREF file that only included the walls, doors, cabinetry, etc. I did not included any notes or dimensions in that file. Now if a change to the floor plans were to happen, it would be applied to both the standard and reverse plans. As for the text, notes and dimensions, I simply added those to the standard orientation drawing on top of the XREF. Once complete, I did a copy of everything with a base point and then mirrored the information on top of the reverse XREF plan. As changes came up, I would repeat the process but in smaller sections since there was some tweaking that needed to happen after mirroring. Primarily with the dimension text being on the opposite side of the dimension line. I did make sure that all my notes, tags, room names were all centered and justified with a "Top Center" or "Middle Center" justification point. That way when I mirrored, things stayed in the correct spot.
I will also add this. Our room names are a dynamic block with a pull down to select visibility states so it says, Bedroom, Bath, Kitchen, Etc. This block was set up with center justifications on the origin. When mirrored, the text stays backwards despite the MIRRTEXT setting. Since everything is centered in the block design, I was able to isolate that layer, select all the tags, and change the "Scale X" value from -1 to 1. This is a pretty quick fix, but only if the block is set up correctly in advance.
I used this process for mush of the project, roof plans, electrical plans, etc.
I'm sure the nature of your project, but hopefully that helps.
