It would depend on what level of care you are actually providing and what benefit you are billing. I am not sure if you are doing regular mental health inpatient or substance abuse. If it is substance abuse, it could be rather tricky, because I dont think the insurance companies have made up their mind on what is RTC and what is inpatient rehab.
If you are billing with HCPCS H0018, than it looks to me like short term residential. If you are billing regular mental health, than I would just use rev code 1002. If you are billing substance abuse. I would double check your authorization letter and blue shields policy manual to see if you are supposed to bill for inpatient rehab, which would be under revenue code 0128. Whether or not its supposed to be inpatient rehab depends on the patients benefit, you facility licensing, what level of care the case manager approved and which ASAM criteria was used to make that determination. If you are unsure, I would default to the 1002 rev code. I tend to refer to the authorization letters that are mailed or faxed to our facility because they will tend to spell it out much more clearly.
I am in Florida so our licensing for Residential 1 beds are closer to inpatient rehab over RTC. However it feels to me like the 2 terms have become interchangeable at our facility (even though I try to correct it at every turn) that is why it can be so confusing.
Hope this helps.