taking other benzo's would almost certainly test positve on a drug test like yours (where pill use is already suspected), the metabolites tested for are shared by all benzos (and possibly benzo related antipsychotics like haldol and seroquil). The test would be able to tell it wasn't
xanax, but the metabolites would still triger positive for benzo's in general.
as for the
Soma question. I'm not a neurochemist, but as far as I know the sites a drug binds to in the brain have nothing to do with what it metabolizes into, and as far as I know Soma shares no metabolites with benzos that would be detected by a drug test. If this were true than Mescaline (and all other phenethelamines like MDMA, 2CB etc.) would trigger positive for
amphetamines, which all affect the adreniline receptors, and this is not the case. So No, Soma should not trigger a test for benzos.
However, taking drugs illegaly is not exactly a smart thing to do if you know you are going to be drug testsed at the expence of your freedom. Public info on drug tests ususally comes out after people start getting nailed, and as more and more hype and hysteria builds around new "drugs of abuse", new drugs are constantly being added to the battery of extended drug tests. If your parole officer has reason to believe you are at risk of abusing pills in general, you will probably be tested for more than just xanax. while I am unaware of any drug test battery that carries
Carisoprodol(Soma) or Meprobomate (another sedative and a metabolite of soma), It dosen't mean they arent availiable. It is certainly possible to test for Soma, and info on its detection period is uncertain. I wouldn't risk it.
Information = Freedom
Soma and Drug Testing 
Linear Mode
