There is no proof that workers with disability have a higher turnover rate than other employees. Indeed, there is even evidence to suggest the opposite, for example a Telstra study showed that people with disability worked an average of 4.1 years in a call centre, compared to a 3.2 year average for people without a disability (Noble 1999).
Job seekers with disability who are successful in finding work often feel they have more to prove and are keen to progress. Sometimes high turnover jobs can be stabilised when employers start recruiting job seekers with disability.
The following link takes you to a page containing a media clip of interviews with employers. These employer experiences support the idea that people with disability stay in the job longer than other employees.
References
Noble, J. 1999 Entrepreneurial Research Project, Telstra Australia.