Given that the Tyranid icon is outside of the Alignment Wheel, and the Necron icon lies within the wheel, is it safe to assume the following: (?)

Necrons can ally with any one force, and that Tyranids can NOT ally with anyone....

Thoughts?

This is stated in the paragraph above the alignment wheel on the back of the learn to play book.

I see. My apologies as I don't have any of the cards or tiles yet.

You can download them from the games support page on this site.

It's on the back cover of the learn to play book.

Necrons can ally with non-loyal, non-signature units. It's not clear if it's limited to only one other faction at a time or if it can be all factions in one Necron deck.

I am looking forward to Tyranids and Necrons. Hopefully they show up sooner later than later.