First, if you're mirroring across the YZ plane, you want to multiply the X value (of the translation) with -1, not the Y value.
As for the rotation, that is more complicated. One hangup is that if you mirror a camera, you would switch its local coordinates from right-handed to left-handed (or vice versa), having the effect of mirroring the image it generates as well. I'm guessing that this is actually *not* what you want, and you want the camera to retain handedness but point in a mirrored direction.
Unfortunately, there's no simple formula that I know of - you're probably going to have to convert the axis-angle representation to a rotation matrix, extract the coordinate axes (forward, right, up), then mirror forward and up (by negating their X component) and recalculate right as the cross product of forward and up. Then put it back into a matrix and convert it back to axis-angle.
If you're doing this in a 3D package's scripting language like Maxscript or MEL, it probably has functions for manipulating vectors and matrices already, so you won't have to worry too much about the mechanics.
Does that give you enough to get started with?