How common are diversions to high-latitude airports for intercontinental flights? Comments to this question point out that diversions and emergency landings are not the same.

Many flights between Europe and North-America pass over (very) high latitudes and cold climates such as Greenland and northern Canada.  How common are diversions such as this one?  Or, more specifically, out of all scheduled passenger flights between Europe and North America, how many are diverted to high latitude airports?  For the purpose of this question, I am considering incidents where passengers were forced to leave the plane and change to one or more other planes, rather than a flight that lands and takes off again continuing to its final destination without passengers deplaning.
Very very uncommon. Goose Bay, Canada, is a diversion airport for US-Europe flights. If you search Aviation Herald for "goose", you will find about 2 to 3 flights divert there each year.


3 flights diverted in 2017:


Delta A330 Oct 20, engine problem 
SAS A340 April 16, low cabin pressure 
Air France A380 Sep 30, engine structural failure


2 flights diverted in 2016:


Virgin B787 Nov 22, engine oil leak  United B767 Sep 15, generator/APU failure


3 flights diverted in 2015:


American B757 Sep 30, electrical problem 
Delta B767 July 31, generator failure 
United B767 June 12, flight controls


2 flights diverted in 2014:


Delta B767 Aug 9, engine problem 
Delta B767 May 1, engine shut down

In all these incidents except for 2, the report in Aviation Herald states a replacement aircraft was required. Sometimes the delay was 6 hours, sometimes the next day. In the 2 other incidents, it's unclear if a replacement aircraft was required or not, but in both cases maintenance was required, so at least a delay occurred.

This compares with a bird strike, or fumes/smoke in the cabin, almost daily somewhere. It's much rare than even lightning strikes, of which 25 were reported in 2017.