Using MTB shoes for road pedals depends on two things: 1) bolt pattern on the shoe sole, and 2) clearance within the lugs (teeth) along the edges of the sole. Many MTB shoes have an SPD bolt pattern. Depending on the shoe, it's possible to use a narrow SPD road cleat (like Speedplay) with some "dental work" on the offending lugs with a Dremel tool.
Conversely, it's possible to use a MTB cleat and light MTB shoes, e.g., Speedplay Frog and Louis Garneau shoes, on a road bike if you need to "live" in the MTB shoes, like on a weekend bike and hike tour. I do this in Japan, where I need to walk comfortably when not riding the bike.