Tranplanner,
For a ton of information and informed opinion on the possibilities & pitfalls of BRT, LRT, streetcars, and transit systems in general, including examples of all of these done right and done wrong, check out
http://www.humantransit.org. The author has designed and consulted on multiple transit systems, and studied many more. Thanks to what I've learned there I'm warming to the idea of busways, especially "rail-ready" busways, for corridors that don't require the capacity of rail, don't yet have the funding for full rail, or don't have the travel patterns that best support rail.
For a nice detailed breakdown of a rail corridor's costs by trackage, signals, tunneling, etc., go to
http://studio.design.upenn.edu/hsr/node/81. Download the "Appendices" and peruse Appendix A.
As for Curitiba, they still have the entire original busway system, and are studying conversion of the busiest corridors to light rail, with consideration also of subway, b/c the busways are at or approaching (and on some lines over) capacity. OT: Robert Moses was a major consultant on the design Curitiba's highway system, of which Sr. Lerner's busways are a major component. I don't know if Moses was involved in the busway part, considering his disdain for transit and people who use it.