Yes it is possible, that you access the vFiler by using the SDK. In Perl f.e. NaServer::set_vfiler is responsible for that. I used something like this:
my $s = NaServer->new( $hostname, $ontapi_major_version, $ontapi_minor_version);
$s->set_vfiler($vfiler_name);
...
You'll find further information in the manage-ontap-sdk - it's worth the download: https://communities.netapp.com/docs/DOC-1152
I used it to develop several Nagios Plugins for NetApp, which are capable of checking vFilers thanks to this API. See http://netapp-monitoring.info/en/
Hope this helps, Ingo Lantschner