while ARIN just doesn't consider anycast IP prefixes in any special way, it's just a regular IP prefix.
From my ARIN account I can't access the current request forms yet, so cannot confirm or deny a standard procedure to request anycast space.
But again, even if ARIN has no formalized possibility to assign number resources for this purpose, then I think they could do so by exception, as normally you'll need to justify 100% of the requested space.
So just because there is no special label, I doubt they are assigned trough regular requests.
Anyway; $ whois -I xxx is an example of a recent requested prefix for anycast assigned by ARIN
Myself, I operate my own anycast (v4 and v6) in PI IP space, and for a customer 4 anycasts (v4 and v6) using RIPE anycast space.
You'll find RIPE's anycast space at $ whois -r 194.0.0/24 and up, and $ whois -r 2001:678:1::/48 and up (and at one point there is a constant gap).