I think there are 2 differenct issues here. First a cable operator is not allowed to encrypt a digital TV signal that he provides over his system if the same channel can be received with an antenna in your area. So if you have an ATSC tuner either in your TV or a separate OTA ATSC tuner then you can obtain the local OTA channels with basic cable service.
Secondly there is the issue of what local OTA digital channels a cable operator is obligated to provide, with the exception of not currently being required to carry more than one channel from the same network I do not know which channels he has to provide and hopefully someone else will provide the information on those laws.