The quiet unveiling of a new bike-sharing program at Georgia Tech last week provided an occasion for the usual self-promoting speeches by corporate types and grip-and-grin photo ops with elected officials. But if the little-publicized event leads to the successful results its champions are rooting for, it could come to represent one of the more auspicious of a recent series of watershed moments in Atlanta's fitful, foot-dragging development into a bike-friendly city. With viaCycle and City Hall are hoping to expand the program beyond Georgia Tech into neighboring Midtown and downtown.