I bought tickets for my kids through AAA (my husband and I have annual passes this year). There was an alpha-numeric code on the back of the AAA ticket that I used to link them to our reservation through My Disney Experience without any problem at all... but we aren't within our window for fastpass+ yet, so who knows what will happen when it comes up.
ETA: realized I didn't answer the question completely... they were real tickets, not vouchers.