A number of people have pointed out that the code I posted previous only works with older versions of the EyeX software [for the record, it was written using: Tobii EyeX Engine (0.8.17.1196), Tobii EyeX Cpp SDK (0.23.325)].
I have updated the code, which now works with the latest Tobii software [Tobii EyeX Engine (0.8.17.1196), Tobii EyeX Cpp SDK (0.23.325)]. This code, including precompiled versions of the .mex binding for both 32-bit and 64-bit Matlab can be found here (see section marked: “Tobii Eye-X Binding”).
Happy tracking!