It might be ok by phase 4 when the players are locked down. But to get to that stage it will be extremely difficult.
It's not difficult, it's inconvenient. Basically players have to self-isolate for two weeks before training camp, during camp and then go in the bubble.
I guarantee if all the players took precautions, masking in public indoor spaces, keeping to bubbles of 5 or 10 people and social distancing they would not spread covid to each other during voluntary training.
It's nothing more than lots of families have done especially if they have immunocompromised members.
But I get the impression that it isn't happening, certainly according to social media Matthews at least was out and about partying. Again I don't know how reliable that is.
But even on the Hawks there's photos of Toews with his arm around fans unmasked. Like don't do that.
Again it's not difficult, it's inconvenient. I just don't think the players care enough about coming back to give up those conveniences.