In our lab we routinely amplify cDNA from lambda phage and we have cloned
many genes this way. We usually heat 1 to 3 microlitres of phage (with
titres ranging from 10e5 to 10e7 per ml) to 70 C for 10 minutes then add
all the other reagents as usual. I think you should easily get
amplification by this method. Our libraries are 2-3 yrs old at present
and still working fine. Have you tried using vector specific T3 and T7
primers? you should see a nice smear. Best of luck.