CATV systems are closed systems, which must not leak or radiate the signals. This is particularly important because CATV systems commonly use frequencies that are used for aircraft communication and navigation.
If you interconnect the CATV system with your antenna, expect a visit from the CATV company, the FCC and FAA. Have your check book ready and pack an overnight bag for your stay at a government run resort were they'll help you get your mind right. (Cool Hand Luke, 1967)
Even if you don't radiate any CATV signal, The CATV system is likely using the OTA frequencies received by your antenna. There will be mutual interference which will make the conflicting signals from both sources unwatchable. Also the OTA DTV signal format is different than the CATV DTV signal format, your tuners can typically be configured to receive one format or the other... not both at the same time.
Re. HOA rules prohibiting TV antennas: http://www.fcc.gov/mb/facts/otard.html The short answer is your HOA and local government are restricted from interfering with your reasonable steps to receive OTA TV signals.