This is the only BMI reference I could find related to acts performing covers in nightclubs; maybe they're sensitive about it? Note it's distributed on the basis of "surrogates."
"BMI collects license fees from thousands of music users in addition to those listed in this booklet. These "general licensing" music users include, but are not limited to, hotels, restaurants, nightclubs, sports arenas, theme parks, airlines, jukeboxes and retail stores. BMI may choose an appropriate surrogate, such as radio or television performances, for the distribution of the fees. In such a case, general licensing revenue serves to increase the rates payable for other performance types which we determine are representative of the universe of performances of music used in general licensing categories.
BMI also reserves the right to use surrogates when accurate distribution data is unavailable. However, we strive to distribute license fees derived from specific users of music to the songwriters, composers and publishers whose music is performed by those users. At any time, we may add a distribution source that was previously unmonitored, if accurate distribution data subsequently becomes practically available."
