I'd have to agree with the pvc tunneling idea. I did this for my
sprinker system and it worked great. You can buy the nozzle head that
you attach to the pvc pipe in the sprinker section of any home
improvement store.

This also saves you the hassle of having to patch over the driveway
after you lay down the wire.

Tunneling under an expansion joint is recommended to prevent cracks
from forming from voids that your tunnel caused.
Hope this helps.

Herb