TROG-2 or even the previous TROG is not perse designed to examine English proficiency in people learning English as L2. But surely you can adapt them, for the fact that it is by far the most extensive receptive grammar tool. My suggestion is, administer it on about 30 people (in the same age range you are targeting possibly) who you consider are proficient English speakers. Keep that as a standard for yourself, and compare your EFL learners scores against it to have a objective measure of their proficiency.
You may be also interested in adapting the work of Dr. Prema K S Rao (link below), who had a very nice way of using priming speed/accuracy as indicators of L2 proficiency. She will be happy to respond to you, in case if you are interested.