Hi Derek,
SessionStartInfo.BrokerSettingsInfo.ServiceOperationTimeout is used to set the timeout to support long running SOA calls. Default value is 1 day.
For the WCF client proxy as you mentioned, you still need to set client.InnerChannel.OperationTimeout to make it work.
In HPC R2, we introduce BrokerClient to help you send/receive SOA calls. If you use this API, you will not need to set anything and it just works (if the calls are less than 1 day). If your SOA calls are longer than 1 day, you will need and only need to
set SessionStartInfo.BrokerSettingsInfo.ServiceOperationTimeout for larger time period.