The method calcProductPriceRule in Mage_CatalogRule_Model_Rule can be used to apply product rules on a specific (custom) price. Unfortunately, this method does not apply the rules according to their priority. In my opinion that is because the method getRulesFromProduct() within the corresponding Resource-Model-Class does not add a "order by" condition.
Does anyone know if this is by purpose or just a bug?
PS: We do need to manipulate the price based on complex configuration options - that is why we want to call the calcProductPriceRule-Method.