Walt Disney Imagineering has announced the first park to receive a clone of Mickey & Minnie’s Runaway Railway while also subtly announcing a ~ 6 month delay for the not-yet-open original:

Quote Originally Posted by Disney Parks & Resorts

Disneyland park guests will be able to step into a cartoon world and join Mickey and his friends on Mickey & Minnie’s Runaway Railway, coming to Mickey’s Toontown in 2022!

This first major Mickey-themed ride-through attraction at Disneyland park will put you inside the wacky and unpredictable world of a Mickey Mouse cartoon short where anything can happen! Once you step into the cartoon world of Mickey and Minnie, you’ll board a train with Goofy as the engineer. Then, one magical moment after the next leads you to a zany, out-of-control adventure filled with surprising twists and turns.

Mickey & Minnie’s Runaway Railway is also planned to open at Disney’s Hollywood Studios in Walt Disney World Resort in Spring 2020, however; special details will make this amazing attraction unique for Disneyland park guests.
Although the exact location of the addition to Toontown was not announced, it has been previously reported that the attraction will be added as part of a small expansion re-claiming backstage areas and the Gag Factory store.