Generation III-V
Focus Energy now increases the user's critical hit ratio by two stages instead of one.
Via Bulbapedia
The chances of Critical Hits are done in stages. There are five stages of which the Critical Hit percentage is calculated. All moves are on Stage 1 apart from a handful on Stage 2. However, with various items, abilities and a combination thereof, you can reach Stage 5 and have a 50/50 chance of hitting with a Critical Hit. Below is a list of the stages and their chances of occuring.
Via Serebii
Brick Break itself doesn't seem to have an affect on crit rate, so it would react to Focus Energy as any other move would.
Bulbapedia
Stage Gen II-V Percentage Gen VI Percentage Gen VII+ Percentage
1 6.25% 6.25% 4.17%
2 12.5% 12.5% 12.5%
3 25% 50% 50%
4 33.3% 100% 100%
5 50% 100% 100%
So, one Focus Energy would take you to two stages, which is a 12.5% chance in Gen 4.