(A friend asked me to post this)
He will be in Rio de Janeiro on NYE and wants to know if public transport will be running and if so, until how late in the night.
OK, December 31st is not a public holiday in Brazil but January 1st is. The Wikipedia article on Rio de Janeiro states in the public transport section that buses run 24 hours, but the metro runs a Sunday service on public holidays (new years day happens to be a Sunday next year anyway)
Rest of week metro service: 5am - 12am
Sunday metro service: 7am - 11pm
The "Get around" section of the Wikitravel article has some in-depth information about getting around Rio like last carriages on the metro being women-only. There is also a full run down of how the taxis work.
Several of the visit Rio sites which, I won't link to as I'm not sure if they're factual so much as outright marketing material, suggest that getting away from the main attractions on new years eve will be extremely time consuming and one should find a club to 'wait it out', they also note that several beach-front hotels offer buffet breakfast 'very early'.
Useful stuff I found along the way:
I'm Brazilian and I live in Rio, and I can tell you from first-hand experience. Buses do work on New Year, but if you plan on taking a bus to either go to the most crowded spots, or to leave from them after the fireworks, keep in mind it will be slow. Painfully slow.
Anyone going to Copacabana beach after 5~6pm of Dec. 31 will experience traffic jams and they get more MASSIVE each passing hour and will return to normal only around 6-8am the next morning!
The subway stays open but on a system where your ticket works only within a small time window... That is, you buy a ticket that can be used only, let's say, between 9pm-10pm of Dec 31st. And another that can be used 5am-6am of Jan 1st. And these tickets are sold a few weeks/days before NYE. And there are long, long lines to buy them. And not all subway stations are open on Dec 31 / Jan 1st.