Disclaimer: ex-BMC
AO is mostly about integrating Remedy ITSM , monitoring, etc) ; it also can fill the role of a general purpose orchestrator . It is comparable to HP/OpsWare's Operations Orchestrator, or Microsoft SCOM, or Vmware vrealize Orchestrator.
In the open source tool chain world we don't have an equivalent tool, because that's what scripting languages are for.
The only real reason you'd use it is if you have other BMC tools at your company since AO might make the integration easier. It's a rather unwieldy installation and has numerous quirks. though the main BMC field dude that stands behind it (Volker) is awesome.
Cheers
Stu