Speaking strictly from experience, I've been notified directly from the court that my client has had a positive blow; the client was also aware of this, so it appears to be done rather quickly. Regardless of what one may be able to "get away with" as far as drinks and testing, my advice is to avoid the temptation and strictly adhere to the court's conditions of release, as the alternative would be spending your time behind bars, rather than at them.
In an update to my question, I actually went to both BI and 2WM today and asked this very question. Both agencies assured me that they make immediate attempts to contact the clients, and it appears court notification occurs within a matter of a day or two.
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