I can tell you the addresses on the PC version (0xCFF45C). I don't think it translates directly to the PSX. That points to the data in memory that you're looking for.
Found these pointers for psx. Thanks for the help. PC version has 2 pointers: 0xCFF444, 0xCFF45C and PSX version also has 2 pointers.
I think the memory structure it points to goes something like this:
0x0 - word; overall encounter rate
0x2:0xD - words; 6bit encounter chance/10bit formation value. There's a chance that these can be encountered "preemptively".
0xE:0x15 - words; special formations in same format as above. Checked first in order. I believe they are two preemptive followed by one back attack and one side attack. Those formations cannot be overriden by preemptive, but can go up/down in probability of encountering with preemptive materia.
0x16 - word; probably nothing. Likely an alignment buffer.
It looks like this:
0x00 - byte; may be enabled/disabled, encounter group 1
0x01 - byte; overall encounter rate
0x02 - battle 1 (0x02 - 0x0D - 6 words)
0x04 - battle 2
0x06 - battle 3
0x08 - battle 4
0x0A - battle 5
0x0C - battle 6
0x0E - back attack 1 (0xE - 0x15 - 4 words)
0x10 - back attack 2 (according to the Makou Reactor)
0x12 - side attack
0x14 - attack from both sides
0x16 - word. alignment
0x18 - byte; may be enabled/disabled, encounter group 2
0x19 - byte; overall encounter rate
0x1A - battle 1-6 (0x1A - 0x24 - 6 words)
0x26 - 4 special formations (0x26 - 0x2C - 4 words)
0x2E - word. alignment