Since it uses the same LGA 1366 CPU socket as in the MP5,1, I don't see why not. Besides there is at least one MP5,1 user posted the GB results here. As expected, the single core performance is rather weak, but multi-core is good due to its 12 cores, but slightly worse than the performance of the E5645, the lowest grade of 12-core MP5,1 that Apple ever offered.
I don't know where you live, but at least in the US, the used X5650 has much better price/performance than that of the L5640 on eBay, except for the power consumption.
