Make sure they are in the same pickup group, and use the call pickup feature.
In the sets make sure the CLS is set to PUA and then configure the RNPG as the same number for both 1111 and 1112. The last thing to do is to add a RNP key on 1112, or look in LD 57 for the FFC for RNP, usually this is #7.
Now when 1111 rings, you can press the RNP key, or get dialtone and dial the FFC, to get the call.
Hope this helps,
Scott M.