New legislation which allows telecoms firms to put equipment on private land would have lost Wyre Council thousands of pounds a year.
The authority was making £5,266 a year from land in Siding Road, Fleetwood, which has been a small telecommunications base station serving the Fylde coast, for years.
But the introduction of the Electronic Communications Code would have seen that fall to £432 a year, figures released under the Freedom of Information Act showed.
The council initially refused to why the land was being sold, who to, and for how much money, citing the need for "confidentiality of commercial information".
But The Gazette obtained details of the deal, which was drawn up behind-closed-doors, and can now reveal that the lease for the site started in July 2002 and ended more than seven years ago, on July 30, 2012.
Since then the lease has been held over, the council said, with chiefs deciding to sell it to Cornerstone Telecommunications for £15,000 earlier this year.
The land was valued at "£15,000 having regard to the impact of the Electronic Communications Code" by an unnamed senior surveyor, the council added.
It did not say how much the land was valued before that legislation came in at the end of 2017.
In a restricted council report, Marianne Hesketh, the director for performance and innovation at Wyre, sought approval to brand the land "surplus to the council's operational requirements" and to "dispose" of it.
Approval was granted and the land was sold on Monday, June 24 "on terms agreed by the council's senior estates surveyor", documents showed.
"The land was previously on a lease agreement which was due to expire," a council spokesman said.
"The land is governed by the Electronic Communications Code, which dictates what the land can be used for and says that it must be kept as a site for a communications tower.
"Rather than continue the lease agreement, the decision was made to sell the land," which is on the corner of Siding Road and Navigation Way.
"The money will be used for future capital investment in the borough."
Under the Electronic Communications Code, landowners are "restricted in their ability to charge premium prices for the operators' use of their property", according to legal firm Ashfords.
It said: "Typically, the sites in question are a small area which hold little value to the landowner as bare land and have few other suitable uses. As such, it is likely that rents paid and compensation awarded will reduce."