That sucks dude! That probably means that on the pre-delivery inspection where they take it on the road test they to had not realized that the tires were low!
I would carefully go over your rims and make sure there is no damage what so ever! not even a little mark or put it back on them to replace them either under warranty or due to their F*** up!
Sorry to hear about another negative experience with a new purchased Nissan.....I wish I had the money or know how to own a dealership my service and sales would be 100% better then "The List" of bad ontario dealers.......
hope u get to start enjoying your Z ASAP!!!!