Reflecting Pool + Nimbus Maze

[Anusien]

Q: If I control a Nimbus Maze and a Reflecting Pool, can I tap Reflecting Pool for or .
A: No, only if you control a Plains or an Island.

This is new, and Official.  I didn't notice it when it changed, but it's relevant so I'll post it here and make sure people know.

It is, but in a different way.   If (and only if) you could tap
another land for X _right now_, then you can tap Reflecting Pool for
X.   Don't overthink it

If you control a Tainted Peak, but no swamp, then Reflecting Pool can
tap for colourless... because that's all the Tainted Peak can generate
(you can't play the other ability).  Likewise, River of Tears can
generate Blue before you play a land, and Black afterwards... so until
you play that land, Reflecting Pool can generate Blue; afterwards,
only Black.

In effect, the Reflecting Pool "looks forward" (just a little) to see
if that kind of mana would be produced by the other land.  That's why
replacement effects such as Reality Twist (see below) and
"self-replacement effects" such as River of Tears, are taken into
account.

[Anusien]

The original ruling was about half wrong:

The reason for the delay is that I was hoping to provide more
information about the exact reasoning behind the rule.  Rulings
without explaination tend to result in a flood of followup questions
anyway... so it's important to understand why Reflecting Pool treats
Tainted Peak one way but River of Tears another.

The difference is in the templating (the exact wording, on the card)
-- one is a restriction on when the ability can be played, the other
is a self-replacement effect.  In the end, the decision of what is and
isn't included in the definition of "could produce" is up to the rules
team, and that's what we use to differentiate.

* It DOES take into account replacement effects (Reality Twist) and
self-replacement effects (Rain of Tears)
* It does NOT take into account costs on the mana ability in question
(Crystal Quarry, , etc)
* It does NOT take into account play restrictions (Tainted Peak,
Temple of the False God)
* It does NOT take into account other possible futures (Playing a
land, a Blood Moon, or a Stone Rain)

So, yes .. controlling a Tainted Peak means you can get R or B from
your Reflecting Pool, regardless of whether you control a swamp.

One last thing that Reflecting Pool does not consider is how MUCH mana
is produced by the other land's ability.  Gaea's Cradle can produce
more (or less) than one mana... but it's not relevant here.  If you
control a Cradle, you can tap Reflecting Pool for Green whether you
control a creture or not.

So something with a self-replacement effect like Rain of Tears will change what Reflecting Pool can provide, but Tainted Peak will not.