It will not fit. The EFS series are specifically designed for bodies wth smaller sensors and consequentially (big word for a Sunday morning
) smaller mirrors. The back of the lens projects into the body beyond the mount and would interfere with the mirror. This lens would therefore only work with 20/30/40/300/350/400/D not 5D or 1series. That is what I have read anyway.
Roger
PS. I see that some of the Sigma lenses also say that they are designed for smaller sensors too.