In the WireTap documentation included with the current downloadable release (2007-1019), the manual says:
The WireTapNodeHandle::getAvailableMetadataStreams function is used to
obtain the metadata streams that are available on the current node.
First, there's a mismatch in the capitalization: Metadata should be MetaData. But this also doesn't match the API headers, where the method is called (more logically) getAvailableMetaDataStream()