Well i think that it all depends how long alliance lasts and how strong it is....
If both parties have strong history and if alliance had been proved more than once both in battle and through
diplomatic actions in RP sense.... I think they can share low level technology ... and with exceptions or limitations high level tech too...
That alliances don't come over night and it takes both sides to be fully prepared to engage technology exchange.
This kind of alliances are very rare.... only my opinion...