it is a federal crime for the CC to charge you extra to receive FREE HD channels. Fact!
you do not have to rent the CC box in order to receive these free HD channels nor but their HD pkg: Fact (as long as you have the correct tv)
"Digital cable ready” (or “plug-and-play”) televisions are also available. These can be used to receive digital cable TV (and often HD over cable) without a separate set-top box. A CableCARD is needed to watch certain cable programming. These televisions do not work directly with satellite - you still need a set-top box to view satellite programming. " http://www.dtv.gov/shopgde.html
i think you are missing the point of the OP.
if your cable company carriers your local channels in HD then you have access to them regardless of level of service; no need to pay extra unless you want the HD channels not offter OTA.