The e-mail address linked to that YouTube channel with all of that HD footage is jack.day@wildbrain.com, according to Jack's LinkedIn page, he's "Senior (YouTube?) Channel Manager at WildBrain".
Domain info about wildbrain.com says that it's managed and hosted by Interactive DHX Media.
Domain lookup info here:
https://whois.icann.org/en/lookup?name=wildbrain.comAccording to the WildBrain website itself, they're "the media company
managing the digital rights of some of the most popular children’s television series ever.
We’re part of DHX Media and manage a
collection of over 12,500 half hours of high-quality children’s TV".
That's a pretty good explanation as to why and how they have such good quality video footage, and why the videos are still up on YouTube.
DHX Media:
"DHX Media is a Canadian media production, distribution and broadcasting company.
Formed in 2006 by the merger of Decode Entertainment and the Halifax Film Company,
the company is a prominent producer and international distributor of children's television."
I'm not that good with legal stuff, but I found this interesting
