--> Copy the PLUS config file "PlusDeviceSet_Server_NDIAurora.xml" (see directory E130-Daten\Navi\Navi-Bugsquashing\TestDaten\PLUS) to your PC
--> Open it and change the xml-tag
<Message Type="TRANSFORM" /> to <Message Type="POSITION" />
--> Save the file
--> Use the modified and saved config file when doing all steps of task 1 of the OpenIGTLink checklist till the action step "Connect and Start Tracking"
--> When clicking on "Connect" of the TrackingToolbox, MITK connects to the PLUS-server.
--> In the MITK-Logging: You can see that MITK receives periodically POSITION-data messages from the PLUS-server. However, the connection process results in a MITK error:

MITK-Logging:
core.mod.igt.openigtlinktrackingdevice WARNING: Received invalid message.
core.mod.igt.trckDevicesourceconfigurator WARNING: Cannot create tracking decive: The number of tools in the connected device differs from the tool storage, cannot add tools.

--> Despite the fact, that MITK receives POSITION-data messages from PLUS, it isn't possible to track a tool via PLUS (server) through OpenIGTLink in MITK (client) when using this data format.

Tested this with PLUS v. 2.2.0 and 2.6.0
Comment: Sending POSITION-data messages from PLUS (server) to 3D-Slicer (client) is working without any problems.