Mark,
OK… so I guess it works… 
But is it ‘webMethods magic’ for territories and gateways? or is each broker server a logical host definition?
Which would mean you go from one cluster service controlling the brokermon process to multiple cluster services, one per broker server instance…
And are all the details for setup called out in the HA doc? I was skimming and didn’t notice … or is this the ‘magic’ of Professional Services? 
Ray