I could actually reveal the dbus interfaces, but it seems I couldn't get the specific way to launch a plugin UI only.
Code:
signal void com.nokia.AccountsUI.Closed(bool AccountCreated)
method void com.nokia.AccountsUI.CreateAccount(QString ServiceType, QStringList Actions)
method void com.nokia.AccountsUI.Launch(QString ServiceType)
signal void com.nokia.AccountsUI.Launched(QString ServiceType)
method void com.nokia.AccountsUI.Open(QString ServiceType, QString StartPage, QString EndPage, QString Title)
method void com.nokia.MApplicationIf.close()
method void com.nokia.MApplicationIf.exit()
method void com.nokia.MApplicationIf.launch()
method void com.nokia.MApplicationIf.launch(QStringList parameters)
method QDBusVariant org.freedesktop.DBus.Properties.Get(QString interface_name, QString property_name)
method QVariantMap org.freedesktop.DBus.Properties.GetAll(QString interface_name)
method void org.freedesktop.DBus.Properties.Set(QString interface_name, QString property_name, QDBusVariant value)
method QString org.freedesktop.DBus.Introspectable.Introspect()
/home/developer $ qdbus com.nokia.AccountsUI / org.freedesktop.DBus.Properties.GetAll