Can a ballista be fired once per round with a crew of three?

The rules for the ballista on p.255 of the DMG state that to make an attack the weapon must be loaded, aimed and fired. Each of these takes one action. However, could each of these actions be performed by a crew of three, with one character to perform each step, thus allowing the ballista to be fired once per round?

My assumption is yes, but there’s nothing textual to support this. Am I missing something?