Sercos 3 (iii) with Linuxcnc?

I've just purchased a 2008 Weeke Vantage 33 cnc router from scrap. The machine is in good condition and I'm going to convert the controller to lcnc.
The servos are Rexroth Indradrive and as best as I can tell they're using sercos iii. My drives have a fiber ring connection rather than Ethernet but the logo definitely says sercos iii. Apparently there were some iii drives made with fiber connections. 
The io is all Beckhoff and the pci card in the pc is beckhoff also. 
Is there any workable, straight forward way of controlling these drives using lcnc and, perhaps, the beckhoff pci card? 
If so then great, much better to use the hardware as is. 
If not then I'll go down the path of selling the rexroth drives and motors and buying Delta or something along those lines. 
Any info of advice greatly appreciated.
Cheers

What's wrong with the PC?

Pictures would be helpful to visualise the problem.