If a term of your probation was 'submit to random drug testing' or anything of that sort, there is a decent chance they can/will give you a drug test when you check in with probation.
If you have a dirty test while on probation, that can be a violation of probation and you expose yourself to additional jail time.
There is no way any attorney could/should give you serious odds. No matter what the odds are, it's not worth it. Get help for your substance abuse problem before you wind up in jail or worse.
Law Offices of David Shapiro 3555 4th Avenue San Diego, CA 92103 (619) 295-3555
Based on your possession conviction, I would expect the recommended conditions for your probation to include drug testing, and for it to begin even as early as at your orientation or shortly thereafter. That is unless your attorney worked to have that condition eliminated at sentencing. If you test positive, probation will likely impose a minor penalty such as work service or refer you to the prosecutor. This would raise the risk of a probation violation charge, and if proven you would face minor (e.g., work service) to major consequences (e.g., jail time).
This information should not be taken or relied upon as legal advice. No attorney-client relationship or privilege is established by this communication.
Testing is almost certainly a condition of your grant of formal probation. As such, it is random and can be required of you at any time - even at your orientation meeting. If you test & the results are positive you will more than likely have your transfer to Hollywood cancelled. Timing would play a large part in what happens to you. Since you have not actually been assigned to a probation officer here in San Diego, there may be some time between the results of the test becoming known and your transfer to Hollywood. If you do get the opportunity to go, tell your new PO about the dirty test and follow whatever instructions he/she gives you.
That being said, I agree with Mr. Shipiro - you need to get into some kind of rehab to help you with your addiction issues. This will only get worse if you don't get the help you need now.
Your situation sounds as though you need a lawyer. Rather than get advice on the Internet, please contact me for a free consultation and we can go over everything in detail. My website it below. Thank you and best of luck.