Beware - long reply!
Greatnan some offenders who are not deeply entrenched in their abusive behaviour, and want to change, will respond in varying degrees to treatment. Part (and a very significant part) of the treatment is in deconstructing the content of deviant sexual fantasies and teaching distraction, avoidance, spoiling, and other strategies to banish the sexual fantasies as they flit into their thoughts. If you can imagine a probation officer specialist asking you to hand over your most deviant and arousing sexual fantasy so they can ruin your surefire way to an orgasm, you can rate for yourself how unlikely that is to work with someone who doesn't want to change. They won't hand over what we would sometimes call their 'bottom-drawer deviant fantasies' - the ones that always work.
The problem with abusive priests is that they can be indoctrinated into corrupt sexual behaviour as they are already proved to have been indoctrinated in at least one other way (that may be contentious for believers in the faith). 100% of abusers have been abused in some way themselves (being abused doesn't predict you will become an abuser - far from it) and being corrupted into sexually predatory behaviour against children means you are likely to set out to corrupt others. By corruption, I mean experiencing horrendous sexual abuse and eventually learning to gain sexual gratification from it. Priests who abuse seek protection from others, and usually get it - if they disclose abuse in their church, everyone will be investigated, so it's safer to keep abuse quiet, which means the opportunity for treatment is lost.
Some treated priests can be kept safe, and their risk reduced, but that means them disclosing the context in which they have abused, where they have been, disclosing names and which seniors knew but didn't act - no point treating and putting them back with a senior in the church who won't challenge suspicious behaviour and ensure they stay away from children.
The majority of prisons now offer sex offender treatment, and all probation services. It is cheaper to treat a sex offender in prison than to release them untreated and at risk of being reconvicted for further offences. It isn't too expensive now - it costs more in hidden costs of services for victims throughout their lives - depression, alcohol and drug abuse, self harm etc. Some see it as expensive because the amount of 'dosage' needed i.e. treatment hours applied, means that longer prison sentences have to be handed down to enable them to complete the treatment. 240 hours of treatment for a predatory paedophile will not necessarily effect a change if they are deeply entrenched. As a comparison, one-off sexual abusers who regret their behaviour and want to avoid doing it ever again might only need 60 hours of education and therapeutic intervention.
If every priest who abused was offered treatment, and the safeguarding children guidelines were adhered to, it would significantly reduce the number of future victims and men who are sexually attracted to children would be less likely to be allowed into the priesthood.
Frankly, I don't think he's even that interesting. 
