Would you expect a plumber to put up plastic to contain dust for a basement bathroom rough-in?
I will tackle this from three ways.  


I work as a general contractor when doing flips.  I would hope to remember to put up plastic or block off areas.  First because I do not want things in other areas to get damaged and secondly because I can allocate someone I am paying $15 an hour to do this.
If I didn't think ahead... I don't have 1 plumber out of the 5-6 I use that would ever let this happen.  First they would get fired on the spot.  Second they are just good guys that care about their job.  They would give me a call and say "Hey you don't have this area ready, you want me to wrap it for you?"  And often they are chuckling because they know their time is 5-6 times what I would pay someone else.  I might tell them $40 for a wrap - but guess what they would do it anyway.  
In my area if there was work done to part of your house that caused damage to another part then the person doing the work would be held liable.  I have seen your EXACT case happen and it ruined not only electronics but also expensive clothing.  This plumber could be sued.  Unless he stated in his contract that his job could expand into other areas and things could get damaged unless XYZ happens - he is liable.  That is why he is bonded.


My last point.  Why the hell would a plumber be doing the jackhammer rough-in by himself?  I always hire a laborer to help plumber with this and sometimes two guys.  It is not rocket science to bust up concrete and it certainly isn't plumbing.  These laborers would have covered things.  I know if I am in someone else's home doing work that keeping their house clean is #1.  You should be really pissed and this is 50% on the plumber and 50% on the GC.  If the GC is paying the plumber he is liable to fix your damages.  Depending on your relationship with him I might just bring up the issue and then try to resolve it after the job is over - and hopefully before your last check to him.

Note: And this is me ranting because of the lack of accountability that the other answers seem to have for the trades...  It is NOT the homeowners responsibility to have expertise in how you will do things or how "things work".  If a plumbing rough-in needs to be done the owner has to completely understand the method of excavating?  Also give me 2 20-year-old guys and a few sledgehammers and we can rough-in a basement bathroom 40 feet away from stack in 4 hours with minimal dust.  How the hell is a homeowner supposed to know what might happen when an expert is doing their job.  If they understood everything they wouldn't need the expert!