While you can use apt-get in RPM distros the backend server that this is connecting to is one that serves RPMs not debs (Unless it is a completely custom install which most likely functions poorly). Typically combining packages from multiple distros is a bad idea even with alien et al because the applications are compiled with very specific shared library versions that are specific to the distro that is providing the packages. The only time it makes sense to use other package formats is when you are downloading a statically linked program that (more than likely) a company is distributing. Even then they usually have tarballs of just the statically linked application.
If you absolutely need an application that isn't available for your distro chances are the source is and you can create your own rpm/deb package, compiling it on your distro instead of hoping someone else's has enough in common with your distro that it works. While this is a bit more work, the hardest part is figuring it out for the first time.