Hi folks - former Fastly VP here.
I've flagged this thread to my past colleagues who may not be on the list. Generally speaking, most routes from AS54113 were always available on any given IXP route-servers. Some additional anycast routes can be announced selectively via communities. Respecting the selective peering policy - bi-lats are provided for somewhat bigger traffic peers, and then of course PNI's for the really big stuff. Some of this depends on serving capacity at any given POP.
Certainly, "big" is subjective, as is "worth it". Nevertheless, there was (and I'm sure still is) mutual performance and cost incentive to peer everywhere that it makes sense, and where technically feasible to do so.
Hope you all get a reply in short order.
Cheers,
Ryan
Disclaimer: things may have changed - my message here is not authoritative on current policy posture. I am not replying on Fastly's behalf.