To clear cap, sure. Frolik would be a Byron-lite at worst; brings speed, PK skills and some offensive upside, although a little less in the speed and the offensive upside but, not by tons, I would say.
However, the 3.4M off the books immediately VS the 750K for Frolik could provide the team, along with paper transactions by then, a potential 6M+ rental for a long playoff push at the trade deadline.
It would have been far from catastrophic to lose Byron on waivers, especially if he had been grabbed by a non-Canadian team. A direct rival picking him up Ould have been somewhat more annoying, with Byron coming back to face Montreal regularly with a chip on his shoulder and something to prove.