In this case, it’s 2 differents sites. they are on the same physical place but you have 2 BCF and 2 sites declare on your network.
You can decide for example to privilege 1800. For example: 900 take the traffic only if you have -90dbm on your mobilephone.
You destroy you intratalk and you mix your ultra (one part for 1800 and one part for 900)