Johan Björnfot talked about this here.
"The scheduler service have been removed. Existing scheduled jobs however will still function. They will be executed on the site. A common misunderstanding regarding scheduled jobs are that they are executed in the Scheduler Service, that is not true the job is executed on the site (this is true for previous CMS version as well). The windows service was responsible to keep track on when a job should execute and then make a request to the site to execute the job,
This has now been chnaged so the site itself keeps track on when a job should execute and when that is time it calls the specific job.
The change though is that with the previous scheduler service (windows service) the service could start up the site in case it was down. Now you need to rely on other mechanism to make sure the site is up, could be a third party ping service or AlwaysRunning mode in IIS."
Workflows in EPiServer 7.5 are built on Windows Workflow foundation 3.5.
WWF is self-contained in EPiServer and does not rely on outside services.
Does anyone know if Scheduled jobs in EPiServer are reliant on ony services installed on the server hosting the site. I don't think they are but am not sure how they would know when to run with out some kind of scheduler.
Similar question for workflow - what triggers an instance?