They could still be on the easement if the easement states it extends through the middle of your yard.
Many people never examine their easements and have no idea where they are. In some cases, they have even built homes which obstruct an easement because they didn't have a good understanding of where the easement was located.
My suggestion is to take your deed as well as any other documents you received when you purchased your property and have a local real estate attorney read them to see if they can determine where your easement runs. If they can't, then they may send you to a surveyor to see if they can tell from the legal description of the easement where it is located.
You can also contact the cable company, but I've never found the utility companies to say anything except "we're on our easement" when you ask them, even if they are wrong.
Just so it's clear, an easement does not have to match your neighbors and can extend quite a bit further into your property. This usually happens if there is another utility, such as a gas line, already on that easement, or if a house wasn't built at the same time as the others.