In effect, yes. The Signal Corps had posts of observation tasked with capturing contrabands ( CSA signals). Tapping into CSA telegraphic coms was routine. At night, a human with normal vision can see a candle at a mile. The longest visual signal recorded during the Civil War was sent by turpentine torch. On very cold clear nights, Fort Transit Station ten miles east of Murfreesboro TN signaled directly to Fort Negley in Nashville. That is 41 miles.Did Grant have huff-duff? ;-) Leigh lights?
An excellent source for the Signal Corps / AoP is the 10 Volume Photographic History of the Civil War. The photos of the hugely tall signal towers is eye opening. The Signal Corps is a part of the war that few if any CW enthusiasts have any understanding of.