There's one important thing to note:
Depending on a pre-release makes the produced package itself also a prerelease.
It makes sense that by default pre-releases are ignored when defining the version range of dependencies because it would alter the version of the package being produced (without knowing which version to pick).
Ideally, the algorithm that checks for the version range of dependencies during installation performs a check whether the consumed package is a pre-release or not, and then either includes or excludes pre-release dependencies within the allowed version range.
I'm not sure whether this is currently the case, but looking at your question I don't think it is. You might want to log a feature request (or submit a pull request?) on http://nuget.codeplex.com