According to Dish, I live in one dma, while only 30 or so miles from the towers of the next dma. I subscribe to locals and get the info for most of the ota channels, just not all of them. One of the channels I do get info from is a channel that Dish does not supply. According to most of the posts here, I am not supposed to get them, but I have had them on on every HD model I have had including the 6000, 811, 921 and two 622's.
Dish is trying to supply guide info for all Locals (at least for your DMA). It doesn't matter if they carry it or not. And they are trying to carry the subchannels as well. Once you get to smaller locals it is hit or miss. Certainly for major stations, if your not getting info, try asking them to add it. It may show up eventually.