Suppose there are two random variables $A, B$ constrained in the intervals $A \in [a_{min}, a_{max}]$ and $B \in [b_{min}, b_{max}]$.
$a_{min}, b_{min} \leq 0$ and $a_{max}, b_{max} \geq 0$.
I calculate the maximal possible distance between $A$ and $B$ like this:
$d = \max \{ b_{max} - a_{min} , a_{max} - b_{min} \}$
Is this correct, and can it be generalized to more than two random variables (with the same constraints).
Your answer is correct.
I think you should define exactly what do you mean by the generalization. But, if I have understood correctly, what you are looking for is
$max\{(A_{max}-B_{min}): A,B \in W and A\ne B\}$
where $W$ is the set of the random variables.