First, my experience is based on working in a high school which may be different than at the elementary level. However, the best experiences that I have had working with the special education teachers are when they involved and are a part of the regular classroom as well. As you said, students can benefit from both teachers so in general we cannot think of general ed teachers and SPED teachers as two separate entities. I have two SPED colleagues that that are engaged in some of the day to day planning of the regular classroom and that makes a world of difference. They know the daily plans and I know also what they are planning on their end in the resource room. One of those SPED teachers coteaches with me during one section and we try to balance the instructional load. So what I would recommend, is become involved in the planning to the extent that you and the general ed teacher feels comfortable. Share ideas to involve you in the classroom and how you could be utilized to provide differentiation opportunities for all students.
Good luck with your student teaching and go Knights!