I first ran into the Easy Rock/EZ Rock branding when Telemedia was still around, at the end of the last century. After all the dust settled in ownership changes, Astral appeared to have exclusive rights to its use.
A quick check and I see a bunch of Astral stations in B.C. (e.g. - Salmon Arm) and the Niagara region of Ontario still using the EZ Rock moniker. And a bunch of Ontario stations owned by Rogers (e.g. - Sudbury) using it.
It just seems odd that such a brand crazy company as Astral -- the word "Brand" is in nearly every middle management job, at least on the Radio side -- would allow a competitor to use their Brand.