Particles are rendered in front of tree billboards

I have searched thoroughly and have been able to find a solution that draws particles correctly relative to tree billboards. One suggestion was to set the renderQueue for the particle materials to <2900 which draws the particles behind the billboards as it should, but then the opposite issue occurs where near particles are drawn behind distant tree billboards.

Any help would be greatly appreciated.

PS I also looked at the Bootcamp demo to see how they did this, but was unable to figure out what was being done differently.

Thanks in advance.

After looking further into the bootcamp demo, it seems that their effect is achieved with a custom tree billboard shader.