That is a good question. The answer is, Yes.....depending on your mbod selection! Some MBODs support both technologies. Example: Gigabyte X79-UD3. So, it's important for you to remember this when selecting your MBOD. Make sure that it states in the specs that it supports Crossfire AND SLI technologies.It should look somthing like this: Support for 4-way/2way AMD CrossFireX/Nvidia SLI technology. Then, make surwe that the MBOD has at least 2 PCIE 16 slots if you are going to use two GPUs. Also, your MBOD should come with the bridge for connecting the 2 cards. Good luck!
P.S. AAfter seeing which MBOD you are using, it does appear that you could make it work, as long as you can find the corect drivers, etc.