I am positive you can! The main things you have to be aware of...they are not very heat tolerant, so you must make sure they are kept watered. The type of Lilac is very important. Getting a decent sized pot is a must. The Lilac will naturally "dwarf" itself based on the pot size and the pruning/trimming it receives, as it helps balance the root growth and prevent it from becoming rootbound.
Keep in mind, too, that good fertilizer is key with growing anything above-ground. I have had container gardens for the last 6 years. This year is the first summer where all of my plants are technically in the ground. My DH built raised beds to get all the containers off the patio and it is rather odd for me.
at 11:02 PM on Jul. 28, 2009