$VerbosePreference is set at least to "Continue."cmdlet, and read VerboseRecord instances from the Streams.Verbose properyExample in powershell script:
ps> $ps = [powershell]::create()
ps> $ps.Commands.AddScript("`$verbosepreference='continue'; write-verbose 42")
ps> $ps.invoke()
ps> $ps.streams.verbose
Message InvocationInfo PipelineIterationInfo
------- -------------- ---------------------
42 System.Management.Automation.Invocat... {0, 0}
This should be easy to translate into C#.