I think this more answers the second question but in David Simon and Ed Burns' "The Corner", a non-fiction book about life in the city of Baltimore, he discusses the origins of the brown bag. In the 1950s and 1960s an increasing number of municipalities passed laws forbidding the consumption of alcohol in public areas. Police officers, sworn to uphold the law, began spending an inordinate amount of time enforcing these laws against public consumption. Drinking on the stoop, so to speak, was cheaper than going to a bar or pub regularly. Additionally, with the urban poor generally confined to medium and high density housing, most people did not have the luxury of a private backyard to retreat to as would have been the case in the middle-class suburbs.

When the police were forced to attend to and cite every individual they came across drinking alcohol in public, it cut into the time the police could spend concentrating on more serious crimes that were prevalent in the inner city, such as robberies, burglaries, assaults, rapes, and homicides. Although the origin is unclear, at some point many of the urban poor began to simply put the alcohol containers into brown bags and as Simon puts it a "civic compromise" was reached. Police now had a sort of plausible deniability with regard to what was in the bag, and the bag's owner would not appear to be flaunting his (albeit low level) civil disobedience. In essence, "live and let live" became the name of the game with regard to public consumption in the inner-city.

Although hardly an academic source, Simon and Burns' later television program "The Wire" also included the back story to the brown bag phenomena in its third season episode entitled "All Due Respect".

Source: The Corner: A Year in the Life of an Inner-City Neighborhood by David Simon and Ed Burns