Unfortunately, tubes are not owned by anyone. They are tiles. Therefore, they are either visible to everyone, or completely invisible.
Also, if you manage to remove the tube graphics from the game, you can use the 'terrain type' mode on the mini map in combination with zoom to find tubes. Heck, you could even select 'destroy' on your earth worker and just pan around the map looking for a spot. My point is, the tube graphics have really no impact on game mechanics, the game will still tell you where they are in many ways.
It would be a good idea for an extra option though.