I went a bit further into the question, and found this interesting pdf from the 173rd Fighter Wing of the Air National Guard. Document is listed as "AFD-130517-091.pdf", it is dated May 17, 2013, so it is not what I would call current with the events being watched. You can access this document at this link. Here is an overview:
A potential reason that there is no new restricted airspace over Malheur is that they do not need it yet. Consider if you will that SIGINT and LLVI (low level voice intercept, a subset of SIGINT) do not have to operate right over a signal of interest. They rely upon line of sight (LOS) so they can operate in relative safety and obscurity.
What then might be able to operate in the area of the existing MOA structure? Would that provide adequate cover? The JUNIPER MOA structure, depending if the extension is in effect or not would put a SIGINT collection asset about 20 miles west of the NWR. If the older boundary is what is active, then maybe 50 miles out. A likely candidate would be the RC-12 GUARDRAIL common sensor platform. If this is the case, you would see something like this.
The product data sheet does not really give you the real capabilities of this superlative bit of kit, but I would venture to guess that the following listed capabilities would come in handy:
"Greatly improved ability to find and track multiple HVTs simultaneously over challenging terrain and dense urban environments, with a single aircraft
geo-location accuracy and speed to greatly enhance full-motion video effectiveness"
Now, COULD a RC-12 be used at a stand off distance of 20-50 miles to collect all the comms of the group occupying Malheur NWR? If it CAN'T, I'd say Congress has wasted a ton of money. I would venture a guess that crews would use this as a training opportunity provided the right EO12333 supporting documentation and top cover were provided. An RC-12 could orbit at a distance for hours at a time, it is a mission profile it was designed for. For a description of the avionics, see here.
Given the endurance of the RC-12, it would make no sense to base it close by. Of course, the closer you are, the more time on station you get. No such thing as a free lunch. I doubt that any Commander would risk damage from basing out of a dirt strip, it just would not be worth it in my opinion.
Looking further into the public news releases, as of 2012, the Army inventory of the RC-12X model stood at 14. They have even helpfully put in a pamphlet how the ground station and RC-12 fit into the architecture.
The RC-12 feeds data to the OGS (AN/TYQ-224), into the DCGS-A "cloud".
There may be other variants out there, the -X is the latest, though. Defense-update indicates that "The US Army operates 48 R s in six units, each operating a different configuration of the aircraft. These include the R N Guardrail I, R P Guardrail II, RC-12H Guardrail III, RC-12K Guardrail IV, RC-12D Guardrail V and RC-12Q Guardrail Common Sensor." It would be reasonable to expect these variants to be tailored to specific target sets in the RF spectrum. The typical Guardrail system deployed to a battalion includes eight to 12 aircraft that fly missions in sets of two or three.
If you are interested in following up with more information on the fascinating GUARDRAIL system, go read this pdf over at fas.org if you REALLY want in the weeds:
Given what is known of the communications of the Malheur occupiers, application of RC-12 to their signals of interest is rather like smashing a mosquito with a sledgehammer. I stick by my assessment that this really is most useful as a training exercise for RC-12 crews, if they are in play. The RC12 is the Cadillac of Army SIGINT aircraft. Now if you see one of these, you know what it is. The highly esteemed blogger Sparks31 wrote about catching a RC12 GUARDRAIL electronically in this post.