I can't say about the cell tower triangulation. Presumably the phone could send its list of nearby towers and has to keep that list updated anyway to stay connected, so that should be a minimal effect.
The next question is why only iPhones? Presumably the cell operating companies have the same information from their end of the connection and could make it available for any phone number on request without any impact on your battery life. Of course being phone companies it would cost $5/mo to keep 3 services informed and if you informed a 4th then it would be $0.25/update for a $1800 overage charge.
I can't say about the cell tower triangulation. Presumably the phone could send its list of nearby towers and has to keep that list updated anyway to stay connected, so that should be a minimal effect.
The next question is why only iPhones? Presumably the cell operating companies have the same information from their end of the connection and could make it available for any phone number on request without any impact on your battery life. Of course being phone companies it would cost $5/mo to keep 3 services informed and if you informed a 4th then it would be $0.25/update for a $1800 overage charge.