Technically they're not over. The cap is not on payroll, it's on total money spent over during the season. A team, like say Philly, could have a $40 million payroll for the first half of the season and then unload $4 million worth of players for the second half and they'd be ok. The same could go for a team with a $28 million payroll for the first half of the season. They could add up to $20 million worth of payroll for the second half and still not go over the cap.
I saw this mentioned in an article last week, but I have no idea where it was.