In my experience interacting with developers - few have a knowledge of Section 508 and even less knowledge of the WCAG. With the WCAG 2.0 being such an intergral part of the Section 508 refresh, it is imperative that all web deveopers have solid knowledge of the WCAG 2.0 and program ground up for Section 508. A study reports that the cost of revision is estimated to be one to six times greater during development than during the design phase and sixty to hundred times greater after release.
Agencies should proactively send developers to section 508 training classes.
In my experience project achieved success with accessibility when developers were provided training with Assistive technologies like Jaws, Dragon and Zoom text.
That really helped them understand the difficulties AT users experience and they created access keys for an technology which was inherently inaccessible.
Education and awareness is the key.