1st: Doesn't have a proper inteligence service.
They have the Internal Security Agency, ABW.
Wasn't this the agency that thwarted the planned terrorist attack on 4 Polish churches back in 2003?
3rd: Is the neighbour of Germany, a country that is a potential target and received almost 1 million illegal immigrants.
Travel advice for Germany states there is a ' General threat from terrorism '. Even Germany is not considered to be high risk.
Poland not being a topdog target of terrorists, the fact that is much more easier to attack the Metro of Warsaw than the metro of London make it a potential target.
I really can't see why they would bother tbh.
Plus there are much easier targets in the UK than the London Metro. Who says they have to pick London? They could choose any large UK city for equally devastating results, and if today's vote on whether to go into Syria goes ahead, that would immediately raise the threat level towards the UK.
Sorry, but I think Poland is pretty much off the map as far as ISIS is concerned, unless of course Poland does something to p1ss them off.