What MMR do Seasonal/Temporary Maps use?

Question

Originally asked on the Riot forums here.

Seasonal/Temporary maps refer to Ascension, Poro King, URF Mode, etc.

Answer 1

"Players have a separate MMR for each queue, each of which evolves independently from the others. This means that your wins and losses in Dominion won’t impact your MMR for Summoner’s Rift."

Source: https://support.riotgames.com/hc/en-us/articles/201752954-Matchmaking-Guide How does Matchmaking work right now -> Step 1 paragraph 1.

++ Without further searches I can also tell you that the Ranked and Normal MMR are seperate.

From the offical article the conclution must be, as "Seasonal Maps" are in seperate queues, that they each pertain seperate MMR that is initially calculated from your normal SR MMR (ref: Ananas [comment])

Speculation: Could very well be that the MMR is tied to their maps, as this is what Riot examplifies after stating they are tied to queues. In which case you could be left with two distinctiones, whether the seasonal goodies are mods of a map or considered stand-alone maps.