I've installed CompuStars into my 2006 WRX, 2010 WRX, and 2011 STI, a friend's 2005 WRX, and many other WRX's and all had AccessPorts and none have had a problem. There just isn't anything that would affect each other.
Let me elaborate on my original reply...2013 STI with AP here and Viper alarm with no issues.