With regards to Blu-ray movies at 50Hz, note that PS3 HDMI output is either 60Hz, or - if your display supports it - 24Hz. Most (all?) Blu-ray movies are encoded at 24Hz, irrespective of whether they are Region A or B.
If your display doesn't support 24Hz playback, then regardless of your actual region (US/Europe/other) there'll always be some kind of pull-down/up to convert from 24Hz to the display rate (50Hz, or 60Hz).
Hope this helps,
p.s. There's a 'Play videos at 50Hz is available' option in newer PS3 firmware, but I believe that's really to allow for videos exported from PlayTV (which, in Europe, are at 50Hz in Standard Definition) to play without any kind of conversion.
As idone says, there's only one firmware that covers all regions of PS3. The region code (for games, and for Blu-ray movies) is held outside of firmware, and is not changeable.