The article says this is a two-year extension of an existing outsourcing agreement for heavy overhaul between PSA and Bombardier, so it's not a new thing.
Envoy, or MQ (the new name for the former American Eagle Airlines - made up of the former Simmons, Wings West, Executive and Flagship airlines) had heavy maintenance bases at San Luis Obispo and Traverse City, Michigan, but I don't know if MQ did any heavy overhaul of its own CRJ-700s. For the longest time, Eagle had just 25 of them, and then got the additional 22 around the time that First Class seats were added.
PSA Airlines put out a press release that did not trumpet the outsourced heavy overhaul of these jets but did say this:
PSA has maintenance facilities in Dayton and Canton, Ohio and Cincinnati/Northern Kentucky Airport and Charlotte, North Carolina.
http://www.psaairlines.com/category/press-release/
That's a lot of maintenance facilities for a small regional operator, but it's all line maintenance and light checks (no heavy checks).
As an aside, the CRJs are awful on the inside compared to the Embraer 175s (personally, I love the E-175s). I've read that the CRJ-900s have a very slight operating cost advantage compared to the E-175s, but I've seen lots of articles pointing out that customers overwhelmingly prefer the E-175s to the CRJ-900s.
