Doesn't it fall to the people who would benefit from an easement to prove the existence of one?

I live in a house that is old, on a street of mostly old homes -- built during or just after WWII. Because of this, there are some weird situations RE property lines and services (water, sewage).

I recently had a weird experience when I tried to sort out issues regarding the waterline. The waterline is actually shared with my one neighbor, and the line splits off between or properties. The point at which that line connects to the city/regional water line is on my property (on my driveway, and so runs partially up my drive before running on my neighbor's property, then splitting off, with the line running to my house running under my driveway to the house).

In doing some checking, with the city (which dictates building code) and the region (which still provides the water service itself), I discovered that it is no longer acceptable to have a shared line. As long as the line is not altered, we are fine, but the minute a repair is done, or change is made, each house has to then have its own water line running off the main line. My neighbors are provided with a dummy line -- a connection all ready for them to use -- on their property. So, if we ever need to replace the water line, we are good to go -- I use the connection on my driveway, and run the line under my driveway, and my neighbor uses his connection, on his front lawn and runs the water line along the side of his house. This seems pretty straightforward and logical. Here is the problem.

Whenever I discussed this with someone from the city (in the Building Inspection department) or someone from the region (the water board), he would always talk about an easement, and how I would have to prove the non-existence of an easement in order to be able to basically deny my neighbor the right to run his waterline -- any part of it -- under my property.

I do not understand this. Surely, if an easement is required for something, it is up to the people who would benefit from that easement (my neighbors in this case) and anyone who would want to work under the assumption of that easement (the city and region) to prove the existence of an easement. The onus is not on me to prove the non-existence of an easement, surely.

Am I right or wrong here?

Please note that, because my section of the community was built so long ago, and even updates of services were done quite a while ago, there is little documentation about how everything is laid out. Even easements may be difficult to find and confirm.

Also, yes, I do plan on getting a full survey next year, because I plan on putting up a fence, and redoing by driveway, which should resolve some serious issues RE trespassing. The survey should reveal any easements (and I know I have one already RE electricity and pole at the bottom of my backyard), but still, why would I be responsible for proving none exist? And, how could I do this anyway? Proving the existence of an easement can reach a definitive if open conclusion -- if you cannot find evidence of an easement after a certain period of time and a certain amount of work, then none exists -- whereas trying to prove the non-existence of an easement is never conclusive.