As far as I understand pRS413 and similar plasmids with Cen/Ars are kind of hybrid self-replicating plasmoids (single copy, contain centromere) that can replicate 200 kbp. That would qualify them as YAC for me ;)
Would appreciate you checking your MTA, but if shearing isn't possible, I'm sure I can find another source.
What other loxP YACs do you have?