BCA allows you to specify a date/time to refresh the report AND a file to watch to kick off the refresh. If you don't specify a file, then the report just kicks off at the appointed time. If you specify a file, then BCA begins looking for the file at the date/time. If the file never appears, the report is never run.
We have perhaps 200 reports that are set to refresh daily -after the data mart is populated. So at the end of the ETL process to put data in the mart, the file watcher file is created. The 200 reports then are kicked off and refreshed at the appointed data/time - as long as the ETL process successfully completed and created the file. A few hours later, a batch job comes along and removes the file for the next day's process so that the reports don't kick off prematurely before the next data load is done.