The signing was originally reported by ESPNDallas.com.
UPDATE: The Ravens have announced the McCann signing is official. Linebacker Prescott Burgess, signed last week, has been waived to make room for McCann on the 53-man roster.
McCann, a two-year veteran, was cut by the Cowboys two weeks ago. He had appeared in Dallas' first two games of the season, recording one pass defense.
"It's a great opportunity for Bryan to play with a Super Bowl-caliber team," Biggins said in a phone interview. "He'll be returning kicks and punts, and will provide quality depth at cornerback and nickel."
The Ravens currently have just four healthy cornerbacks - Cary Williams, Lardarius Webb, Danny Gorrer and rookie Chykie Brown.
Chris Carr (hamstring) and rookie first-round pick Jimmy Smith (high left ankle sprain) have been battling injuries through the first four weeks of the season, and safeties Haruki Nakamura (knee) and Tom Zbikowski (concussion) have recently gone down, as well.
With Webb needing to play a major role on defense, the Ravens also have been looking for someone to handle the return duties. Undrafted rookie LaQuan Williams has struggled in that area.
McCann averaged 20.6 yards per punt return last season (including a 97-yard punt return for a touchdown), and averaged 22.0 yards per kickoff return.
Biggins said that he's been in contact with the Ravens since McCann's release by the Cowboys, but the deal just got finalized yesterday.
Originally signed by Dallas in 2010 as an undrafted free agent out of Southern Methodist University, McCann spent one week with the Ravens at the beginning of last season. Baltimore claimed him off waivers on Sept. 5, and declared him a gameday inactive for its regular season opener. McCann was waived the next week.
McCann re-signed with the Cowboys following his release by the Ravens and appeared in nine games for Dallas. The 5-foot-10, 186-lb. corner posted 15 tackles, and had a 101-yard interception return for a touchdown against the Giants in November.
The next week, McCann was named Pepsi's NFL Rookie of the Week for Week 11 after his punt return for a TD.