There's a SharePoint Timer Job:SQL Server Reporting Services Service Job for SQL Server Reporting Service Application.
However, report subscription info is stored in SSRS database tables: [Subscriptions], [ReportSchedule], and [Schedule]
Further investigation revealed that:
When a report's subscription is created, a SQL Server Agent Job is created
with the same id as the ScheduleID.
The Command in the SQL Job's step
exec [ReportServerDBSP].dbo.AddEvent @EventType='TimedSubscription', @EventData='987dd212-3328-4d77-a358-21644b4bf4d7' --SubscriptionID
The SQL agent's job runs as per the schedule and creates an entry in [Event]
table in the Report DB
In SharePoint, SQL Server Reporting Service Application's polling process
(w3wp.exe process) gets started by SharePoint Timer job, specifically by SSRS
Service Job for SSRS application and then it creates notifications and
processes and delivers the actual report.
Having said that, I now believe, reports get processed as per the SQL Agent job's schedule, not the SharePoint timer job's schedule.