Most craft beer pubs have their own lines installed as no brewery, micro or macro, is going to install lines, at a cost, if you're only putting their beer on for a week.
A micro will only install a line for a pub if they know they're going to be on permanently.
Alternatively, depending on which macro it is, the publican can just drop one of their beers and switch to craft. The macro may or may not take the line out, depends on how lazy the maintenance guy is really. Once a publican decides to drop a beer the macro may leave the line in as a gesture of good will as they know he/she will just replace it anyway.