So many ways - it really depends on the footage you have or the footage you want to shoot.
If you want to now exactly how that one was done, I'm sure that's in the Cinefx mag - I think the whole issue was on Titanic. But its been a while so I don't recall the actual method.
Here's a few ways: (the first one is the most probable as to the way they did it - at Digital Domain I would guess).
1) Shoot your two characters with match frames as close as you can get. Then model or scan the heads of each, Then morph the CG versions of each head so they change from one to the other with lighting and textures and changes in geometry - in that span of time while they are morphing, you can shift your CG camera around so the CG of old rose matches the live action of real old rose exactly. Then it's just cross fades.
2) You could use reshape in AE to do a morph, but you would have to get the two shots lined up really close for it to work well. I would shoot wider than you need but with a larger frame size than you need, then you could move the elements around to get a good match and the edges wouldn't show.
I don't think you need a motion control camera shot here because the frame comes to a standstill during the transition.
3) You could match move a CG versions of Old Rose onto Kate's face and then do painterly reveal through to the CG Old Rose and then another reveal through to the real Old Rose.
4) If you can get your outgoing shot to match your incoming shot you could just do a long cross fade - but the geometry of things like the eyelid are going to change and it won't be as seamless as it is here.
Don't be fooled - a lot changes here, position, rotation, face geometry, wrinkles, eye spacing, skin texture, lighting color and direction, eye texture (which may in fact be CG all the way on either end so that Young Roses irises match Old Roses irises when the actor's own would not have. The blink is the giveaway.)