I don't believe so. I had a chance to mess around with a Galaxy Nexus the other day and I compared the batteries. I believe the Nexus battery is slightly thinner but longer, so it wouldn't fit in the SGSII.
EDIT: However, I do have to caution it was the GSM version of the Galaxy Nexus (the person who owns the phone works for Google) so I am not sure if there was any body modification to the CDMA version Verizon one.
After looking at the thread I referenced more closely, it looks like they are getting the t-mobile version gsII mixed up with the i9100. They probably aren't similar.
I really wish it worked, I would love some hidden gem of an extended battery for our phones. Don't really like those scam batteries on Amazon/Ebay with an extra 5% of battery life.
And I'll take lower battery life over having a brick the size of the 80's cell phones.
That thread makes me think it'd work with the Skyrocket though and not our phones.