This is an NHL initiative rather than the networks. There are 4 ad feeds: one for English Canada, one for French Canada, one for the US and one for Europe (reason why Finns are seeing Russian ads).
Technology behind it comes from an European company that has done it for football matches for 5 years+.
But it doesn't compare to the massive Rolex CGI ad shown on Singapore FI this weekend - basically blocked out the cars racing by.
https://twitter.com/AzmilKamil/status/777130669243715584