It's certainly possible with the demise of the JAR 15 hour minimum. Depends on the candidate's skill when assessed. My conversion to a *UK* ATPL+IR ie pre-JAR/EASA, from an Oz & US ATPL+IR took 9.5 hours - including both flight tests for the licence & IR. The flight test was really one flight done in two halves. We never even left the aeroplane, just mentally flicked a switch after the last landing from the 1st half: "That was the IR test. From this point on we are now doing the professional licence flight test."
The benefit of a combined test was being able to count some test items towards both the licence & the IR. Getting it all over & done with in half a day wasn't bad, either!