I think it's hard-coded but you could easily bolt on some story scripts to augment the progression.

Something like this:
Code
//INIT SECTION:
DB_ExtraTalents(3);
DB_ExtraTalents(6);
DB_ExtraTalents(9);
DB_ExtraTalents(12);

//KB SECTION:
//Add 1 extra ability point on each level up
IF
CharacterLeveledUp(_Player)
AND
_Player.DB_IsPlayer()
THEN
CharacterAddAbilityPoint(_Player,1);

//Add 1 extra talent point on every third level up.
IF
CharacterLeveledUp(_Player)
AND
_Player.DB_IsPlayer()
AND
DB_ExtraTalents(_INT)
AND
CharacterGetLevel(_Player,_INT)
THEN
CharacterAddTalentPoint(_Player,1);

My D:OS Mods:
Dunamis - A 15 hour Adventure Mod for D:OS EE

A Necromancer's Crusade - 10 hour adventure mod for D:OS EE

4 Character Creation (EE)