http://idioms.thefreedictionary.com/go+to+town
go to town (on something) to do something eagerly and as completely as possible
Angie and Phil have really gone to town on their wedding. Usage notes: often used to describe an activity that involves spending a large amount of money.
Oxford bilingual gives,
to go to town on something = tirar la casa por la ventana, no reparar en gastos.
In your context I'd say "cuando se estuvo de acuerdo, se puso a hacerlo de verdad/en serio" or some such "intensive" statement.
In Spain, "se puso a hacerlo yendo a por todas" "con toda la intensidad" "yendo hasta el final" or some such...