Okay, I got around to installing the game and giving a few runs. Screenshots were taken in 1024x768, 1280x1024, and 1680x1050 resolutions. The smaller images were then overlaid with 80% opacity and scaled up to 1050 size height while maintaining the image's aspect ratio. I have done similar to BF2 and the 1.50 patch to test their widescreen implementation. So here's the resulting image:
Even prior to opening these images up for editing, I was able to confirm that BF Heroes is VERT- in handling widescreen, which is not too surprising given how DICE, as a developer, is lacking in sense. It should be noted that development for the game started quite a while before they even bother to consider widescreen. The game itself is based off of the same engine used in BF2/2142 and, as a result, widescreen was never implemented until much later in the game's life.
I would not count on DICE to consider implementing proper widescreen until after a year after its public availability (which was June 25, 2009). And given how they handle development resources, I don't expect people will get the update until Winter 2010. And by then I expect that they have some lame excuse in saying that they ran into issues which won't be out until April 2010.