The home team always supplies an emergency back up goalie and he is eligible to play for either team should the need arise, it's actually an NHL rule.
NHL rules state (NHL rule 5.3.) that if both of a team's goalies are forced out due to injury, a team is "entitled to dress and play any available goalkeeper." And more recently, the NHL has required home teams to maintain a list of available area goaltenders who could fill in for either team in a pinch.
