Ok, so there's a row of houses at the top of the photo (along the street), and there's what I agree looks like an alley between a row of houses at the bottom of the photo. And you're telling us that the "alley" is actually a utility easement. The "alley" runs from the street that runs vertically at the left edge of the photo to a point that is beyond the right edge of the photo. Finally, I understand you to be saying that one of the neighbors (presumably the owner of one of the properties at the top of the photo) has put up a gate that prevents a person from driving in the "alley" from the street at the left of the picture to the back of your property.
All correct?
If that's all correct, and without being able to read the document that created the utility easement or seeing where the actual property lines are, I'd say you have a big problem.
For starters, since the utility easement presumably does not run in your favor, you have no standing to do anything about the gate. Have you contacted the utility company in whose favor the easement runs? I assume that the gate blocks its access, so it might be willing to deal with this. Of course, if the utility company doesn't use the easement anymore, then it might be unwilling to do anything.
You might have a valid claim for a prescriptive easement, but you'd need to sue the utility company and the owner of every property over which your prescriptive easement would run. You could probably, in the same action, sue the property owner who put the fence up to get a permanent injunction against the erection of such a fence. You'll need to confer with a local attorney about this, and the first thing that attorney would need to do (unless he/she knows the answer off the top of his/her head) is whether it's even possible to obtain a prescriptive easement over a utility easement. My guess is that you're looking at a $10k+ retainer and probably a minimum of $20-30k in fees over the entirety of the lawsuit. My further guess is that would be cost-prohibitive for the purpose of preserving the minimal rent for a back house on what appears to be a fairly run-down piece of property.