Sorry for late reply, but I was looking at the E6220 and just doing some preliminary research.
Unless explicitly stated, machines that lack vPro are unlikely to have vPro capability. Whether or not this is relevant to your purchase depends on if you need the additional management (AMT), security (Intel-AT), or other capabilities conferred by vPro. Lattitude E's should still be manageable by Dell's proprietary KACE solution should your IT already use that.
If you need vPro capabilities make sure the system you order explicitly states it is vPro.