Coastarine,
I'm in the camp that thinks peat-smoked malt is required in Scotch whiskey but inappropriate in Scottish ales. If you read Noonan's excellent
Scotch Ale, part of the Classic Styles series, you'll find a very in-depth look at the
real history of the style.
Thought processes like kevmoron's is all well and good, but like most quasi-historical "logic", it falls well short of the mark. Sure, it makes sense to think that fuel would be peat. That assumption would be wrong, because it's logic applied to a lack of in-depth knowledge, even though it's pretty good logic.
The real answer is a little harder and darker: coal. The Scottish ales that in the 19th and early 20th centuries defined the style didn't have peat anywhere near them. In fact, the historical record of peat in Scottish ale can be directly traced to America in the "microbrew revolution" - someone who knew just enough about history to be dangerous thought a little too hard. From thence it went back to Scotland's Scottish ales. After all, if the market wants peat in their ale, you'd be a damned fool to refuse it them.
All that aside, if you want peat in your Scottish ale, by all means add it. I've had smoky Scotch ales and enjoyed them immensely. All I ask is that you don't brew a smoked Scottish ale under the delusion that it's historically appropriate.
Happy New Year!
Bob