Jason pointed out to me (via Omnitech once again) another great improvement coming in BlackBerry OS 10.3 that will really make power legacy users feel at home. BlackBerry has opened up the API that essentially allows call blocking apps to work on BlackBerry 10 just like they did on legacy devices. Essentially what changed is that developers now have access to the incoming caller ID number so they can decide based on that if the call should be dropped. Thankfully BlackBerry finally deemed this crucial API was important enough to release.
PS: The screenshots above are from a quick app that Omnitech mocked up.