We had this very issue. We moved into our house and we were told that United owned the tank and that we were to get gas from them b/c of this. The apparent agreement signed by the original owner was that only they could fill the tank b/c it was United's tank. The agreement was a 3 year agreement that automatically renewed annually and if you wanted to end it you needed to give 90 days notice. You also had to pay a removal fee of $600 AND get the tank out and have it available for pickup (i.e. take it out of the ground yourself). We only started looking into this when we wanted to build a screen porch and we were considering getting close to the tank and were thinking about moving it anyhow.
Then it dawned on us - we were never informed about this tank ownership when we went to buy the house. There were no liens on the house. When we asked the original owner about this afterward he indicated that United told him the same thing - that they owned the tank - and he was the original owner of the house. Talking with a lawyer indicated that this was sometimes done - a handshake deal between the builder and United - so United probably put the tanks in the ground for some great deal to the builder with the idea that they still owned the tank. Who knows how/if the original home purchaser was ever told.
We did try to purchase the tank from United. First we were told not to bother b/c we were promised the owners gas rate - which lasted for one fill only. So we pursued further to purchase the tank. We got told some song/dance that you don't want to do this for liability reasons, how expensive this could be if something goes wrong, etc. BUT they were willing to sell it to us -for more than the tank was valued at new - the tank was now 15 years old. When we did the math on how much it cost for a tank we realized very quickly that it would only take us less than 2 years to recover our cost because of how much United was gorging us in overpricing the gas. When they wouldn't sell us the tank at a reasonable price we started to investigate their actual ownership further. I also contacted the VP in Millersville to attempt to get a reasonable offer for this tank.
United never could prove they owned the tank to us. You see when you own something on someone elses property you are to file a UCC-1 form that indicates this and should come up when someone goes to buy the house (part of deed search) so the home purchaser knows what they will and will not own on that property. We inquired with another gas company they indicated that they needed proof of ownership for legal reasons. We told them the story and also told them that we had the deed to the house - which in our eyes indicated ownership. They were okay with this and filled our tank for us. I kept United informed, gave them notice. Now, with a full tank, United came and locked our tank out and took the regulator on the tank, claiming it there tank. I called the VP again at this point, he understood concerns, and said the sales guy would be contacting us. They did have someone come out and unlock the tank and put the regulator back on. They wanted me to sign for this 'service' both the locking and unlocking. I denied them that - I said I would sign that it was done but would not sign to pay for the service. The poor service guy was almost told to go back and lock it again, but the sales guy finally agreed that he was okay with this, all the while promising no charge for the service. Of course I received a bill for both the locking/unlocking, contacted the VP in Millersville and the sales guy here, asking again for the UCC file - and never received it. At this point they realized they didn't have anything on us. I did not receive another bill and recently checked my credit to be sure they did not report a delinquency. For all sakes and purposes, we now own our tank, but I do fear trying to leave this current company since I don't have proof of ownership outside of property deed and paperwork from both United and our current company that says they are filling the tank at a Customer Owned Tank. I sure hope this suffices if we try to leave our current company. They, too, had us sign a service agreement for x time and also pay for a lawfully required inspection that is ~$100.
Take from my experiences what you will. I do agree that my fear is the folks that don't know any better getting gorged for overpriced gas. I would be more than happy to start a movement to put a stop to this. Even though it is not happening to me any more it is disgusting.