Cool but how does this affect the Leafs?
Subban was originally acquired by the Blackhawks through a previous trade, which saw Robin Lehner being traded from Chicago to Vegas, in exchange for the aforementioned Subban, a 2020 second round pick (which was used by Chicago to select goaltender Drew Commesso), and Stanislav Demin, a left wing prospect currently playing for the University of Massachusetts in NCAA.
Toronto's role in this trade was acquiring Lehner from Chicago with his contract 50% retained, and subsequently trading him to Vegas at 50% retained, allowing Vegas to have the player on their roster for only 25% of his original cap hit. Toronto also sent right wing prospect Martins Dzierkals to Vegas, who is currently playing for HC Plzen in Czech Extraliga. For Toronto's retention, Vegas sent them a 2025 5th round pick.
Toronto would later use this pick in a trade with the Florida Panthers, wherein they traded it, along with a 2020 7th pick, to acquire Florida's 5th round pick to draft forward Dmitri Ovchinnikov, who currently splits games between the KHL and MHL in Russia. Florida would use the 5th round pick they received to draft defenseman Kasper Puutio, currently in Liiga. Florida used the 7th round pick they received to draft goaltender Devon Levi, who currently plays in NCAA and has been notable for his performance in the 2020 World Juniors, wherein he won gold with Canada.
Devon Levi is currently with Sabre, as he was apart of a trade which saw him and a conditional 2022 1st round pick being traded to Buffalo by Florida, in exchange for forward Sam Reinhart.
Malcolm Subban will likely be the Buffalo Sabres backup for the foreseeable future, as Aaron Dell has proved ineffective for the role with Craig Anderson unavailable and Dustin Tokarski retaining the starter position. As Toronto is currently higher in the standings than Buffalo, it is unlikely Subban will see game time against the Maple Leafs, unless circumstances closer to the dates of their upcoming games (the next closest being March 2nd), render other goaltending options unavailable, or his performance whilst on the Sabres deems him a suitable starter for the game.
In short, you asked.