Many Lilac will produce sucker growth that is genetically identical to the parent. When they are about four inches tall they can be dug and separated from the parent plant.

Cuttings can be taken when flowering is finished and the leaves have hardened off. Dirr says that soft wood cuttings dipped in rooting hormone root easily but are difficult to overwinter. Seed have two disadvantages in that they are not likely to be true to their parentage and two have double dormancy. Moreover, seed propagation is not going to render a clone, obviously.
In your area I would say that if you have access to a heated greenhouse or a warm coldframe cuttings would be the best bet. That being said I would also suggest taking and rooting large amounts and hoping that a few would make it through the winter.

not exactly cloning but if u dig all the way around one chain it and rip it out u can plant the pieces everywhere