Wont be many flights a the moment over the poles but the are regularly scheduled under normal circumstances.
The only restrictions on aircraft operations is called ETOPS and only applies to twin engined aircraft (Extended Twin OPerationS). It stipulates the amount of time an aircraft can fly on one engine from an airport it can land at. So if an aircraft has 180 minutes ETOPS then it can fly 180 minutes single engined operation from an airport it can divert to.
Over the years the ETOPS has increased as engines and aircraft have become ever more reliable and the engines for the A350 has achieved 340mins ETOPS which is enough for the aircraft to operate unrestricted anywhere over the globe – so can fly a more direct route from departure to destination airports saving tons of fuel every flight and million of pounds of fuel costs every year for the airline. Not sure the airframe has achieved the same level of clearance, but really I can’t think of a route in the global network that would require that level of ETOPS is ultimately unnecessary.
One of the best things of FR 24 is the feature where you can track where the aircraft has been flying over the past week. These airlines don’t half sweat their assets under normal circumstances.