To debate efficiently, I would start from definitions of three different concepts under BPM "umbrella" (see also http://improving-bpm-systems.blogspot.com/2009/04/should-we-consider-third-forgotten-bpm.html)
BPM discipline, noun
discipline which allows you to model, automate, execute, control, measure and optimise the flow of business activities that span the enterprise’s systems, employees, customers and partners within and beyond the enterprise boundaries
Remark: At present, the BPM discipline is the best way to implement process-centric enterprises.
BPM system, noun
Remark: Any process-centric enterprise has its own enterprise BPM system. The enterprise BPM system may not be perfect (e.g. some processes may be only documented on paper, some details are only “located” only in the minds of certain people, etc.), but it does exist.
BPM suite, noun
coherent set of software tools for facilitating the implementation of a BPM system
So, in accordance with these definitions, business process automation (BPA) is an integral part of the BPM discipline. We implement BPA within enterprise BPM-systems with the help of BPM suites.