Omega Air doesn't own that B707 anymore - they sold it shortly after acquiring it from the USAF in exchange for several B707-320Cs (sorry, I can't remember how many, but I think it was about 7). It is now owned by Raytheon and is currently in storage. I don't know how suitable this aircraft proved in commercial service, but I have read in an article on the RAF's E-3D AWACS aircraft (which have the same engines & u/c) that the ground clearance of the CFM56s is very low, and these aircraft cannot be landed in a crosswind.
This aircraft was built as the production prototype for the E-8 Joint-STARS program (not the E-6 program) and went into service with the USAF with the designation YE-8B. By the time the USAF got the green light to go ahead with the JSTARS program Boeing had already closed the B707 production line, so the decision was made to use ex-commercial airliner B707s instead of new-build airframes. Omega supplied the first batch of old B707s in exchange for the YE-8B, which they registered as N707UM. The "production" JSTARS aircraft, designation E-8C, are now entering service at the rate of 2-3 a year. The majority of the aircraft in service so far (7) are ex-Qantas, along with one ex-Pan Am and one ex-World Airways example. The next batch to enter service are likely to be the ex-Canadian Air Force CC-137 examples.
These aircraft are given a thorough overhaul at Northrop Grumman's Lake Charles, Louisiana, plant to zero-time the airframes and upgrade the electrics, amongst other things. I've noticed from photos that the cargo doors are also removed - which makes me wonder whether some of those retired B707-320Bs at Davis-Monthan with huge chunks missing from their forward fuselages have become the donor aircraft for the required sheet metal?
There was an article in a recent copy of Flight Int'l in which it was announced that USAF was seeking tenders for the re-engining of these aircraft. Engines to be considered included the CFM56 and the JT8D-200. The latter is being proposed by Seven-Q-Seven of Dallas, Texas, a joint venture that includes Omega Air and Pratt & Whitney as partners. Flight tests are currently being done on an ex-Challenge Air Cargo/ex-Lufthansa B707-330C (rego N707HE) at the moment, and certification is expected around the middle of this year. 7Q7 are hoping to get orders from both commercial and governmental/air force operators for their JT8D-200 re-engining program.
Some websites of interest:
Northrop Grumman's ISA division - JSTARS:
A press release from Pratt & Whitney re. re-engining of B707s: