In theory this should work, as they are both implemented in different
binaries and register different extensions with IIS. I also don't know of
any specific problems that people have had.
Here is some conversations on asp and asp.net in MSDN:
Q: Could you comment on interoperability (via Session Objects, Query
Strings, etc.) between ASP and ASP.NET? Any gotchas?
Mark Anders: There are a few. First, we've made the object models as close
as possible. However, if for example you store COM objects (not new CLR
objects) in sessions, and you want those to be out of proc, ...