Are Azure AD Sync attributes exposed to JQL or must the attribute be first mapped to a custom field?

[Chadwick, Mark]

I'm new to JQL and trying to build a filter that will allow our agents to quickly identify any issues that are unassigned and are in their local sites. Azure AD Sync is populating the City details for the reporter once an issue is raised but I can't seem to get to that data in my JQL query. 

Essentially what I want to achieve is something like;

Project = "IT Service Desk" AND City ~ 'City / Site Name' AND Assignee IN (Empty) AND Status NOT IN (Closed, Completed, Canceled, Cancelled, Done, Resolved)

Any help will be greatly appreciated.

Thanks, Mark