Does Bluefire uses ADE? In that case they must have adapted it with regards to the SVG. I suspect they use another engine.
Most readers support SVG to a certain point, only not the more fancy stuff. Also, according to the specs of ePUB2 not the complete set of SVG must be supported. Text-align however should be and I think it is a big mistake from Adobe. If you want to keep the image and the caption together on the same page, this can be used. However, without the align it is impossible to center automatically.