I have the following query which tells me how many documents were retrieved for each customer, but it only works for the "on-demand" customers:
SELECT PatientFacility, LEFT(LocalDateTime,7) as Mnth, Count(*)
WHERE EventType IN ('RecordRequest','RecordRequestBreakGlass')
AND LocalDateTime >= '2016-01-01'
AND LocalDateTime < '2017-01-01'
GROUP BY PatientFacility, LEFT(LocalDateTime,7)