Very unlikely they didn't know it was happening.
For starters, they're claiming it's their "low volume, high quality" products that are involved so we'll assume it's not Heineken but the likes of Fosters or Tiger being passed off as craft. So either the pub was already selling these and started ordering more for their "local label" or the pub ordered these specifically but was only selling them as the local stuff. If the latter the Heineken rep would have come into the pub and spotted their was no Tiger tap and would have asked what the story was. If it was the former they would surely have noticed the increase in the amount ordered and made an enquiry.
The lines would also have been installed and cleaned by Heineken so the "quality team" would have been aware of it (but may not have cared).
My only reservation may be that it was one or two reps who organised it in an attempt to increase their sales without permission from head office. Although there's breweries in the north that are actively encouraging the relabelling of their products up here to shift more kegs so who knows.
