alt Hacker Newsno Miklós Laczkovich's extension as described on wikipedia only says that both of the following questions are proven undecidable:
1) is there some value x such that some function F(x)=A(x)-B(x)=0?
2) is there some value x such that F(x)>0?
while you asked:
> I'm pretty sure it's not decidable if two EML trees describe the same function.
that would be
3) is for every x F(x)=A(x)-B(x)==0?
which Miklós Laczkovich's extension does not provide.
And you ignore the fact that Miklós Laczkovich's extension applies to real numbers and functions...
If it's undecidable whether it's 0 at even ONE point, clearly you can't prove that it's 0 everywhere.
Likewise, if it's not decidable for real-valued functions, clearly it's not decidable for complex valued functions.