The “Blue Spruce” is a very common tree species found in the northern regions in Canada. This said, the “Blue Spruce route” is one which flies over isolated northern areas of Canada, Greenland, Iceland, Ireland, then into Europe.
This route system is commonly used by airlines with fleets consisting of twin engine aircraft, which are not ETOPS certified and/or may not have HF capabilities. These routes are frequently used for ferry flights between Europe and North America.
The most common alternates used for this route are CYFB, BGSF, BIKF, and EINN, although there are many more options available as shown in the link below.
http://220kts.com/ferry-flights/airports/CYFB-iqaluit-airport.html
Once an airline is certified ETOPS by the authorities, it will be allowed to fly further away from suitable airports. This allows for more flexibility and a chance to fly on the NAT OTS.