I am going to try this today (at least the first step):
First: Mix household bleach 1:1 with warm water and a few drops per gallon of dishwashing liquid detergent - only a few drops - as a wetting agent. In a well-ventilated room, mop the subfloor with this mixture. You may see areas where the mixture reacts with old stains expressed as a bit of foaming. What is happening here is the ammonia in the urine is reacting with the bleach to form Chloramine Gas - not pleasant stuff, but it will disspate quickly with good ventilation. This will eliminate the ammonia and destroy any residual urine products.
After this is complete and dry, mix a batch of deodorizing liquid as follows:
One pound of Baking Soda, one quart of hydrogen peroxide, one gallon of very hot water, one tablespoon of the same dish detergent as you used before. Mop this down and allow it to dry. Brush or vaccuum up the residual baking powder that may precipitate when the formula dries.
You should be fine after this. A bit heroic, but if you do not get it all, the next damp day, that dog will revisit in spirit.
Wish me Luck!