Penny signed for Peterborough yesterday on a three-year deal, after some impressive performances in non-league football.
And McCann claims that Posh beat off competition from West Brom to sign the defender.
“I am really pleased to get this one done and credit to the chairman for getting this one over the line," McCann said.
"Alex has shown a lot of commitment to us because there were a lot of clubs interested in him. Credit to him that he wants to test himself in league football and not go into an under 23 Premier League side because I know West Brom were very keen."
Penny is capable of playing at right-back or centre-back, and has great power and size for his age.
The 20-year-old still requires a lot of development, but is expected to challenge for a place in Posh’s first-team over the upcoming campaign.
Penny’s chances of action at Peterborough are likely to be far higher than if he had picked West Brom.
Baggies boss Tony Pulis does not have a particularly strong record of developing young players over the course of his career.
Posh only finished in mid-table in League One last term, and are chasing a play off spot next time around.