I used a Hilton AC award about 3-4 years ago.

We were going to Churchill which only had AC code share so couldn't use *A
miles.

There appeared to be a restriction on type of fare as we had to change
our dates to get the flight but not sure if they came out of the same
bucket as FF awards.

At that time there was a special number I got from Hilton to talk to the
AC specialist at AC who knew how to do Hilton awards and he was both
knowledgeable and helpful. Sorry don't remember the number.