Rule of thumb is 5-6 kegs per tap handle in the market. Figure you might average 2-3 half-bbl kegs per month per taphandle, and you can estimate how many kegs you need.
I think that New Belgium study was right on the money for a regional brewery. For a local outfit, you won't have the buffer of kegs waiting for the freight to make sense to return, so your turns will be more per year. But really, you need to look at how many taps and how fast the beer turns through per tap.