The City of Boston needs all the Police, Fire Fighters, and Paramedics it has out on the streets, not doing a detail at a hockey game. With the poor road conditions, response times are much lower than usual, which means it's vital that more First Responders are deployed in neighborhoods. There's also going to be a rash of heart-attacks as people shovel, and the possibility of criminals taking advantage of the situation to loot. Diverting any City resources to a hockey game that doesn't have to be played is silly.
There's still a travel ban. And the T isn't running. So how would fans get there? You'd be playing in front of a mostly empty house. The only people there would be those who live near the Garden, along with a collection of drunken fools who would only be rambunctious and cause trouble during the game.
It's unfair to ask arena employees to get to the Garden in this crap. And it's unsafe to run an even without sufficient security staff. As well as the afore-mentioned Police.
An alternative would be to play the game but not open the Garden to the public. Then you would't need Police and EMS details. You would't need ticket-takers and ushers. Just a skeleton crew of access point security, media, and personnel from the two teams.