Mountain bikes have been used for longer (100 mile) rides since they were invented. Back then the perception was that these 'balloon tire' bikes were way too sluggish to be used on the road. So to disprove the theory, the bikes were taken out on road century rides. Here is a quote from Charlie Kelley, author of 'Fat Tire Flyer', who did many of these century rides on a mountain bike to help change public perception. I want to add that 10 miles is not very far in 'bicycle terms' and is doable with almost anything, as long as the rider is relatively fit.

VN: One thing I really enjoyed from the book was how you would go out and ride road centuries on your Ritchey mountain bike to promote the brand.
CK: Well, if you’re in a road race, you would never be competitive on a Ritchey bike, but a century isn’t a race and elementary skills and tactics will allow you to keep up just fine. With fat tires, you lose some of the acceleration, and you can’t climb as quickly, but once you get rolling out on the road, the tires don’t make that much difference. So that was a real selling point, that this guy on this bike could finish road centuries in reasonable time. I mean, I worked on being fast, I was never a competitive racer, but it wasn’t a race or competition, but everyone notices who is going fast, and these bikes made people realize that you weren’t giving up that much when riding them, and it was really fun. When you smoked a guy on a Masi, well, he knows he’s been smoked.
Read more at Interview: Charlie Kelly, author of 'Fat Tire Flyer' - VeloNews.com