This was always my take on it if I was a pragmatic, high ranking individual.

"Who cares?"

It's not a question of covering anything up it's a question of why care to begin with? If whatever this is, if it is at all intentionally does things to prevent being observed you won't get any consistent data. It remains a spook, a spectre. Obviously no harm is intended since I have not seen any Cylon Centurians marching down the streets

Meanwhile...

We have things, you know... Real Earth things... Like the Russians. The west seems to have eternally locked horns with the Russians and simply doesn't have the time or resources to deal with anything else. And our Russian counterparts are the same way.

Things must be bad if they’re using the UFO card.