Although I am not familiar with probation procedures in Or, I imagine that the other court will learn of your new arrest. I think that it is important to remember that an arrest in itself is not a violation of probation -- you must be convicted or proven guilty. I'm sure that an Or attorney can answer this question with a little more specificity.
Many probation orders require that you report all arrests to the probation judge. You should read yours and see if it is required. If so, failure to report the arrest would likely be a probation violation itself. Courts have a good deal of discretion regarding probation violations and revocation should only be used as a last resort. You should contact a criminal defense attorney so you can put your best foot forward on this.
You should bet on Newport finding out about your Douglas County problem. You may actually have a probation duty to report it on your own.
A good criminal defense attorney would seek to have your probation violation trail your actual DUI case. That way, if you win the DUI case, the probation violation might just go away. You shouldn't try to navigate these waters by yourself - that's a recipe for disaster.
Your DUII arrest is visible in any computer search run by law enforcement and court personel. You should not take the risk of not reporting this in Newport.
Disclaimer: This is a general comment to your posting and is not a legal opinion or advice. This an informational-only posting. This posting does does not establish an attorney-client relationship. If you think you need legal advice or legal representation for this question or matter, you should consult a licensed attorney in your jurisdiction.