The smokeyness comes from the peated malt.
The yeast is very similar to english ale yeasts.
But scottish ale does not require peated malt to be added to it. I have read a bit of discussion on the matter and nothing concrete is established. Sure, add a touch of peated malt if you like that. From my usage of it in beers other than a scottish ale, I'd say the Wyeast Scottish ale doesn't throw smoky or peaty flavours.
It's historically possible that when Scottish ales were brewed that the use of peat as a heating source for the boil may have imparted some flavour, as may if the crystalised barley was heated in a peat fired oven. Maybe its that wonderful association with scottish malt whiskeys that see people look for a "peatiness"
All I know that I if you like low malty beers, a scottish ale can be a marvellous brew. With or without added smokiness.
Back to the original supposition, yes Beer Belly, London Yeasts and Scottish yeast appear as interchangeable in many britannic brews.
Lastly, scottish ale yeast (and Edinburgh yeast from Whitelabs) is a marvellous yeast that can be used for many a brew. I would consider it one of three essential yeast in my collection (which of course doesn't not include lambics, any thing belgian or wheaty) :icon_cheers:
edit : from the Australian style guidelines comes mention of smokiness / peatiness / earthiness and does mention yeast as an influence on smokiness. Very interesting. It also mentions water .. brew with dirty water to obtain an earthiness .. I wonder ..
Comments: The malt-hop balance is slightly to moderately tilted towards the malt side. Any caramelization comes
from kettle caramelization and not caramel malt (and is sometimes confused with diacetyl). Although unusual, any
smoked character is yeast- or water-derived and not from the use of peat-smoked malts. Use of peat-smoked malt to
replicate the peaty character should be restrained; overly smoky beers should be entered in the Specialty Beer
category rather than here.