You can use a reciprocating say to cut the buckets off down the side, then dig it out and have your hole already pre-dug for them to go into. Mix in some compost and mulch them well. Keep them watered well the first couple years until they take off. I personally have found lilacs to sulk after being moved. They need a location w pretty much full sun for maximum bloom.
If you feel that you tear up the roots too badly, you should cut some of the tops out to even out the top and the root ratio before replanting.
