Yes, self-propelled racing wheelchairs (excluding hand-cycles) and wheelchairs being pushed by a guide are permitted in the Full Marathon, Half Marathon, and 5K events. In the registration form there is a section to fill out to indicate you will be participating in a wheelchair.
The policy of the Austin Marathon is that racing wheelchairs that are self propelled by the participant have a soft start time that is a few minutes ahead of the official start. All other participants must start behind the field of elite runners, and it is recommended that participants seed themselves in the start corral according to their projected finish time, with the faster runners towards the front and the slower runners towards the back.
The athlete must be securely seated in the wheelchair and remain so while racing.