So apparently wilburs limbo was a train station, and I think that its referencing his song jubilee line!
Just think about it, wilbur is stuck in a train station with no other people except for schlatt because they sometimes get caught up in the void.
(Also jschlatts limbo would be a liquor store. Try to tell me I'm wrong, actually either that or it's a club-)
And so wilbur just waits patiently for a train to come by but he's like,
"Well I'm dead and the train is probably the chance of me being back to life so that's not happening-"
Right as dream pulls up on a train and hoping out being like-
"Yo get in loser I'm resurrecting you." While also dragging ghostbur out to stay in wilburs place so that the balance doesnt tip, and wilburs just like-
"Another chance to terrorize a child and a nation again? Sure!" And just like hops in!
And that's what I think happened!