If memory serves, the last time Israel was loaned a cutting-edge radar system, it was before the invasion of Iraq. It was expected that Saddam would launch missiles at Israel even though Israel was not allowed to participate in the USA’s invasion, and so he did.
The Israeli’s are outraged that they are not allowed on the new American military base. There are two reason I can think of for this: the radar is cutting edge technology and the USA does not want anybody to get a close look at it – even an ally. Or, the USA wants to control when the attack on Iran will occur.
If the Israelis had control over this greatly increased capability of intercepting Iranian missiles, they might be quicker to strike Iran. So, it is likely that the USA is following the same policy as with the invasion of Iraq: strike Iran, don’t let the Israeli’s participate, but protect Israel from incoming missiles.