As many fans guessed, that was indeed a Mother Box being used to reconstruct Cyborg's body in Batman v Superman: Dawn of Justice. According to director Zack Snyder the development of the Mother Box and its capabilities in the DCEU was a heavily discussed subject. "That’s the first glimpse of the Mother Box there. It was an agonizing birth. I really wanted to show Cyborg’s birth because I feel like he plays such a strong part coming up, and I really wanted to give a sense of him. I really want [the audience] to know how far he’s come."
Based on Snyder's comments, the Cyborg we see in Justice League Part One will be much further along than the one glimpsed in Lex Luthor's surveillance footage. Justice League Part One will be released next November while Cyborg's standalone film will hit US theaters on April 3, 2020.