We routinely fly jets in the Montreal airspace both VFR and IFR and have yet to come across a serious porblem wrt language. ATC has always been most cooperative in sorting out any confusion and will quickly intervene if a safety issue arises. It seems like an old issue being rehashed for little gain.
As for the VFR french traffic mixing with jet traffic (read fighter guy) in the overhead break at 250 kias that would be an issue at most civilian airports regardless of the language. Breaks look pretty but do little to make life easier for ATC.
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