In the Two Dudes Doc, they talk about Vince meeting Diesel, and sending him to Albany to help Shawn win back the IC belt from Jannetty.

When Jannetty won the belt on RAW, was Shawn always getting it back so fast?  Was Marty's run just to do a surprise title switch on RAW?

If there is no Diesel, does Shawn win it back that quick anyway?

Yes to all the questions.