I was in contact with LANDesk Support regarding this case.
Following steps should be done:
1.) Add the PC with AddComputerEx.
Fillout "deviceName", "type=Computer", ipAdress (any valid IPv4-Address, not important for PXE), IPName and macAddress
2.) If done you should assign the PC to the OS-Deploymenttask
2.1) You can get them with the method (GetProvisioningTemplates)
2.2) If you know the ID you should assign the PC with the Task with the Funktion (AddDeviceToScheduledTask)
If you have none, you should create one.
3.) Start(Schedule) the PXE-Task
Start the Task with (StartTaskNow):
You can Enter the taskid, and optional rescheduleType (ALL is done if nothing entered).
The rescheduled options are:
ALL (starts all tasks)
FAILED (starts task that did not succeed)
BUSY (starts tasks that did not attempt to run)
I think BUSY or FAILED should be the best, so not all deployed PC's will be deployed again.
4.) After this wait a second
.. wait some minutes till the policy is active (it can take a while).
After this reboot and PXE should start.
By entering a MAC and PCName you doesn't need a BARE-Metall Server if you will integrate them by OS-deployment with PXE.