If you use CollabNet's Subversion client (v. 1.6.13), the development libraries are included. For the most current version (v 1.6.17) you may need to install CollabNet Subversion Edge for access to the development libraries.
Sure, the subversion-devel package should not conflict with Collabnet, but it has a dependency with the subversion package, which installs svn binaries in /usr/bin, which takes precedence over CollabNet's path in the PATH environment variable.