Looks like you can under certain conditions.
http://www.apple.com/support/products/faqs.html
Has to be 30 days old or less.
"(ii) With Transfer From Original Covered Equipment to New Covered Equipment. You may
make a one time, permanent transfer of the coverage under the Plan to a new Apple
product that is owned and purchased by you within thirty (30) days of the Covered
Equipment purchase. The new product must be eligible for coverage under the Plan and
at the time of transfer both products must be covered under the manufacturer’s one (1)
year limited warranty. Apple will issue a Plan Confirmation for the new product, which
will then become the Covered Equipment. When notifying Apple of the transfer, you
must provide the Plan Agreement Number, the serial numbers and Proof of Purchase of
the products being transferred by sending or faxing, where available, notice of transfer
to Apple as set forth in the section immediately above."