Yesterday some of the people in the office were heading back downtown on HWY59 between 5:30 and 6:30 and ran into a multi-car speeding crackdown just north of Beltway 8. They reported between 5 and 7 unmarked crown vics with people pulled over.
These are typically used by Harris Country Sheriff deputies.
This is the same set-up I saw on the South beltway two years ago. The white crown vics sit on the backside of overpasses for miles one right after another so you can't just speed up after you pass one.
I left at 8:00 pm last night and there was no sign of them or any action on the scanner but if you live in the metro area and spot a white crown vic working traffic start looking for more.