To benefit the community, posting the answer here:
Regardless of tier, the limit for “GetInstallationAsync” is 60 calls/minute per namespace. You could store the installation state locally. Changes to installations can then be made via update and patch operations.
Given the context of migrating from App Center Push to ANH, the recommendation is to use the new Android/Apple SDKs. The new SDKs will store current installation information on the client device and create/update the server whenever there’s a change, thus avoiding the need to make GET Installation calls.
Chris performed refactoring and extending a table to avoid throttling issues.
Thanks Chris for the co-operation!