Can a frame grabber be used to command a FLIR OEM camera to perform a NUC on demand?

No. The native digital data format for Tau2 and legacy Photon cameras is 14-bit serial LVDS. A serial-in, parallel-out (SIPO) accessory is required to convert the serial digital data into a parallel digital data signal that can be acquired by the PCI-1422 and similar frame grab hardware. The SIPO is limited to passing only digital data, and does not provision for other signals, including camera commands.

This question and answer also applies to the legacy Photon camera models. The Photon product line and its accessories have been discontinued. The information here is provided for historical reference.