I tried for a while, but couldn't get this to work in 2.8.4. I did, however, get just about everything working with Wordpress 2.7.1 using the following links and some tinkering:

Step 1: Description of hacks necessary to make WordPress work inside Symfony.

Step 2: Share user information between Symfony and Wordpress

More code for step 2

Help setting up session database

+2  A: 

I've written a follow-up guide to the helpful article on theodo.fr that works with the latest versions of WordPress and has steps for upgrading: http://blog.codeclarity.com/2009/12/02/integrating-symfony-and-wordpress/. I believe your conflict is the esc_js function defined by both Symfony and WordPress. If you run my command in step 4 you should be good to go with the latest version. Hope that helps.

Fantastic. That worked really well. Thanks for the help.