Does anyone have any experience/knowledge of the cruise control system on a Legacy BL?

It’s been suggested that it’s simply a matter of adding the control stalk and connecting to the brake light switch?

Any info would be greatly appreciated

I'm not sure about your model, but on my 2009 2.0 R Impreza it was just a matter of changing the steering wheel that had the buttons, the connector was there, I just plugged it in and the cruise was working just like that. Hope it helps!

As with most cars that don’t have cruise control it’s normally there as they wouldn’t make lists of different harnesses they use the same one for all models.