I've never seen that with a rated wall either, but have seen wood framed walls designed for deflection with the top plate captured on both sides by blocking and connected with truss clips that allow vertical movement... 

Is it a combustible construction? Did you use metal studs in this wall because of the slip tracks?

I'd probably use a slotted metal top track, and frame the wood stud head within the slots so it can move up and down.  

Look at http://www.clarkdietrich.com/products/head-wall-deflection-systems/blazeframe-fire-stop-deflection-track

Don't forget to ask for a credit due to the swap of steel studs for wood.... also... is your rated partition required to be entirely non-combustible?

Actually I just found a project where I used the track on wood studs. I didn't think too much about it as long as the drywalls are lapping and that is the rating that you are trying to keep. 

great, i like to product mightyaa found, used it on a shoping mall in hawaii a couple years ago. Does it really save signifcatly over traditional track and drywall?  I left that firm before they reached that point in the construction process.

 this is a small, development, a drive thru restaurant with adjacent lease-able area for one or two other tenants.  VB construction