I'll venture a very complicated "Probably Good."

I noticed when I moved from NJ, zone 6b to AZ zone 7b that roses which normally sailed through winter in zone 6 could sometimes fail here in zone 7 due to a western peculiarity in weather. I notice that we have a lot more periods of time in spring where days are in the sixties or seventies and nights are actually freezing. Or worse: we'll have stretches of weather in early March in the eighties and no nighttime freezing and then in April we'll get a night at 15F. Turns out this is really hard on roses, especially young ones. So to your point, Z5 Utah weather might test a rose more than Z5 New York weather.

I see that Eugene Desgasches is rated to zone 5b. I guess some bourbons inherited a good measure of hardiness from their damask lineage which might provide some protection not just from low temperatures but from the kind of yo-yo weather described above. If the hardiness rating is based on actual data, then I'd bet the prognosis for zone 5 would be good, provided it's grown on its own roots, mulched generously in fall, given a bit of protection from north winds, and given plenty of sun. As for Typhoo Tea, I'm guessing its rating of 7b is a default for hybrid tea roses, and that its heritage includes some cold-hardy roses that help bring it protection. If it grows in a western, mountainous zone 5, then there's a good bet it would survive eastern zone 5 winters.