Ok, its not an easy solution but it works perfectly (on any digital desk with only one solo bus for that matter).
Step 1: Soft patch your monitor bus outputs to the digital 2 track out
Step 2: Use a short XLR to jump the AES 2 track out back into the AES 2 track input
Step 3: Soft patch the AES 2 track input to 3 input channels, for example digital 2 track left to 46, digital 2 track right to 47, digital 2 track left to 48.
Step 4: Assign 46 and 47 to the LEFT/RIGHT master bus and pan accordingly, assign 48 to the mono bus. Raise all faders to unity level to send to left, right and mono
Step 5: Patch your IEM Que to the LEFT/RIGHT master bus output and your cue wedge to the MONO output.
Step 6: Make 2 mute groups, one mutes CH 46 and 47 (IEM), the other mutes CH 48 (CUE WEDGE).
Every time you solo something it will be sent out the digital 2 track back in to the digital 2 track which will come up on ch 46, 47 and 48. Use your 2 mute groups to switch between IEM's and CUE wedge.
Make sure to leave the CUE ON MAIN FADER option up so you don't accidentally solo your solo bus.
Hopefully this makes sense. I've done this on multiple tours on a profile and have seen others do the same. Any questions let me know!