Let us throw in another monkey into the wrench. What happens if the job is started at 20 minutes after the hour, and for various reasons ends up running until 45 minutes after the hour? Since the job is running when it is supposed to run at 40 minutes after the hour, it won't.

Please, don't tell me that this will never happen, as the first time it does what then? You need to plan for the possibility.

I'd recommend separate jobs and code each job appropriately.

On the other side, it does appear that you should be able to determine which schedule invoked the job, as I have seen it reported in the history for my backup job. I just haven't figured out how it does it yet. I'll do some more research tonight when I have a bit more time.