Please, notice in the file G4AlphaInelasticProcess.cc that the process G4HadronInelasticProcess is called for G4Proton::Proton() instead of G4Alpha:Alpha(). Therefore, no inelastic process is assigned to alpha particles when the application developer makes use of the class G4AlphaInelasticProcess.
This problem was reported in Bug Report #1309 and fixed in July 2012. The corrected version will be available in Geant4 9.6 to be released this December.