1) to be clear, the RTX software referenced by Rob is the same as the WinAC referenced by JesperMP (called WinAC RTX).
2) When Siemens first released the 1507S, they were saying (unofficially) that at some point non-siemens IPCs would be supported, possibly as a 1509S or something. At some point, they stopped admitting it was even on the roadmap, which isn't promising.
The old system was based on a realtime windows kernal addon, which meant you could do it with any windows PC, because the installer just installed the addon first.
The new system is based on a Hypervisor model, where it distributes the HW of the PC directly to the PLC side and the PC side. My guess is they don't know how to do that for any old PC HW, they can only do it in a deterministic way for defined IPCs.
I think I saw someone trying to install it in a VM once, and it installed, but then on boot the hypervisor had errors and it wasn't usable.