hook_menu() items created in a custom module don't retain the active-trail of the parent tab
OK...so this basically ended up being more of an Open Atrium issue than anything else.  Due to the fact that Open Atrium relies heavily on Features and Context, the style sheet was setup to deal with the classes added by those modules.  Drupal's implementation of active-trail and active classes was working fine, however the theme's 'active' styles weren't setup to work without the classes added by the Context module.

I could either a) add a Context for the menu item added via my module (which is the route I took), or I could have (b) modified the CSS for the theme by adding a custom stylesheet.

Thanks for all the help guys, but I am embarrassed to say that in the end, it was just a bit of a theme problem from the Open Atrium install.