Yup, I've even seen it up near the Scottish borders, but only for growing potatoes and not for a decade or more.
I have to say though that I don't want to see irrigation in FS in the future. Done properly it would be fiddly and time consuming and completely at odds to the flow of the game, so if it is ever introduced I hope it's optional.
I understand it's a major aspect of farming in some areas of the world, but it wouldn't work in the current FS style. Perhaps if Seasons was introduced it would suit the play more, but of all the areas they could expand the game this would be way, way down my list of things to introduce.