When Filoni has spoken of Maul's 'cheating death' (my words), he referred to it as a subconscious thing. Therefore, I'm guessing that it wasn't something taught to Maul by either Sidious or Plagueis. Plagueis was definitely looking to control such power consciously, and in ROTS Sidious implies that he never learned (he could be misleading Anakin, but I never interpreted it that way). Whereas with Maul it's explained as some subconscious/instinctive thing that called upon the Dark Side to keep himself alive despite his mind being completely shattered. The interpretation I put forward before is that I'm guessing Palpatine might be sincerely interested in how Maul survived. Plagueis had not achieved the power to cheat death, as he could not keep himself alive under Palpatine's onslaught of Force lightning. Palpatine even remarks that Plagueis could save others from dying, but not himself. Meanwhile Maul has kept himself alive, something that would be of huge interest to the Sith. I think he might have gone to Mandalore personally to test Maul. If Maul can be killed easily, then there's nothing special about him and perhaps it was just sheer luck that he survived his injuries. But if Maul can survive what Plagueis could not (we do see a very brief shot in the trailer of what appears to be Maul on the ground at the receiving end of Force lightning), then that, IMO, seems like Palpatine would be very interested in studying and a power Palpatine would want for himself. As for Maul's motives. He made it very clear that he aimed to make both the CIS and Republic irrelevant and make a power base for himself. I think he's feeding Sidious a bunch of BS, just because Maul fears him and values his life. Maul even refers to Sidious as the most powerful being in the galaxy in Revenge. I think Maul ultimately wanted to take Sidious out, but he did not intend for Sidious to come for him personally so soon into his plans. And I think the implication of that preview is that Sidious knows he's being lied to, since he looks over at Savage with a curious "hmmmm." There can only be two and by Maul taking on an apprentice it's obvious to Sidious that Maul presumed to make himself a Sith Master and had no intention of being apprentice again. That's my interpretation anyway.