this is what my friend used in his converision (mci) it looks great and has been in for about 2 yrs. so far with no problems. it was bought at a home improvement store, not ikea, its generly called laminate floating flooring
I have some type of laminate flooring in my entry haul way where I live. They have cupped up slightly along the edges of each slat from where the AC condensate over flowed and leaked along the slab under the floor. So a plastic vapor barrier is probably a really good idea for a bus install.
Laminate is a decent way to go but watch out for toxic stuff. Laminate is made in different ways. The cheap stuff is made with HDF (High density fibreboard) which is bound together with a formaldehyde based glue so when your cutting this stuff where a mask! Look at the warranty on the package. If the warranty is less than ten years chances are it's of the poorest quality. Find something with a 20 year or more warranty. Keep in mind with this stuff that if you chip it or damage it it is extremely difficult or impossible to fix without removing the floor. Although the 20 year stuff is very durable! Personally I don't like it much because it isn't real wood (its the purist in me I guess).
There is better quality stuff which is real wood laminated like plywood and is finished with a layer of the finish wood on top this comes in pre-finished or un-finished form but also demands a higher price. These floors are generally easy to install . You can buy a self install kit at Home Depot or Maynards for like $20. Make sure you use the underlay and leave room around the edges for the floor to expand and contract. These edges are then covered by base board or the like.
Perhaps the stuff from Ikea is decent as for toxicity as Ikea is generally fairly responsible but check any way.