Happy you asked that question, kickballpro, because I actually discussed that very subject with him earlier this week after reading the thread. The conversation was not on air. Here's what Stull told me:
1. He never turned down an invitation to the MWC
2. He thought the MWC and CUSA would merge a few years back during conference reshuffling and UTEP would join the MWC as part of the large superleague. UTEP would not have to pony up an exit fee in that case. This story of the two leagues joining forces received some national pub, but it never came to fruition.
3. When both SDSU and Boise State temporarily left the MWC for the Big East 2 1/2 years ago, there was an opportunity for UTEP to pursue a move. But, Stull said at that time, he was more worried about the MWC's future since the perception was the league was on the verge of disintegrating with Boise and SDSU leaving (hence the talk of the superleague with CUSA). At the same time, San Jose State and Utah State were so worried about the WAC collapsing that they jumped to the MWC even with Boise and SDSU leaving. Then, Boise and SDSU reneg on the Big East because they realized their TV deal won't be what they thought it was (with so many schools leaving and the new American Athletic Conference formed) and the MWC let them back in. By then, they already had SJSU and USU as expansion teams so the door was closed to UTEP.
4. UTEP will still entertain a move when the next TV deal expires and this happens all over again.