My understanding is that DCC actually operates at a fairly low "speed" of data transfer compared to modern network systems. In other words, it carries a lot less data per second than the cat 5 data systems used in computer networks and such. Because of this, the DCC wiring is not as critical when it comes to cross talk and interference. The lower the data transfer rate, the less susceptibility to problems.
I am using Digitrax but I haven't used it that much yet because my layout isn't complete. I do have the wiring under my 70 feet of shelves "finished". For the track feeder bus, I am using #12, for the feeds to the track off the bus I am using #18, attached to the track about every 4 to 5 feet. The #12 feeder bus wire is located at the back of the shelves. The 6 conductor flat cable used for the loco-net connections is run near the front of the shelfs. This keeps them seperated from 18 to 24 inches. So far, it has all worked great with no problems.
Although I feel the DCC systems are fairly immune to interference, it still makes sense to keep the data-bus away from the feeder bus or any other power conductors.
My 2 cents, but take it with a grain of salt because I am pretty new to this.
One other thing... I was working on the layout one night while listening to a baseball game on a portable radio I had set on the layout shelfing in close proximity to the loco-net bus. When I turned on the Digitrax system, the radio emitted a continuous high-pitched squeal, at first I thought the Digitrax system was about to explode! Then it dawned on me what was happening.