It's kind of interesting in terms of analytics... can we predict when lenses will appear and disappear, from our perspective? What might we do with that information once we are more advanced?
2. Unless we find faster than light communication (which, with our current understanding of physics is about as likely as humans jumping to the moon) there is nothing we could use it for other than definite proof that other life has evolved in the universe. Interesting data, but they're most likely extinct for billions of years already and even if they're not, the compound gravity lens will have moved out of alignment by then so we have no means to send a message back.