It uses a project add on named Paged Geometry :
incredibly optimised/fast for massive plants , trees on terrain,
even more dense than Oblivion and really fast/smooth !

perhaps more than in Crysis ??

http://www.ogre3d.org/phpBB2/viewtopic.php?t=36655

Look at videos in the topic , they are incredibly great

If only 3DGS could have such quality add ons ??
That's not Conitec team that will bring such things , they have enought work
with all forecast things that are in it since one or more years

Well Ogre3D is a top 3D engine and is become more advanced each time.
Don't compare Ogre3D releases rate with 3DGS ones
Should 3DGS become open source ? i laught

I think it's possible to use it with 3DGS , caus that's open source.
But i doubt the author to be interessed to port it ...