anacron requires /usr/bin/run-parts from crontabs. However, this file should probably be put in a differnt package anyway, since it should be possible to install only anacron (and not also vixie-cron).
Still present in anacron-2.3-15
Still present in anacron-2.3-16
anacron-2.3-17 still requires vixie-cron.
I don't see any technical reason for requiring vixie-cron. Anacron does not seem to need it. For a home pc which is turned on in the morning and turned off in the evening cron is not needed.
Still present in anacron-2.3-25
I added a requirement for crontabs in anacron-2.3-27 and dropped the vixie-cron requirement in anacron-2.3-29.