Analyzing this RF circuit
It's just been so long that I don't know how to begin with the
  topological analysis that would let me frame it mathematically


Firstly, ignore the parallel tuned circuit formed by L304 and C303 (just for a little while why I look at the series tuned circuits)

A 1.5pF capacitor in series with a 15nH inductor is a series tuned circuit at 1.061 GHz: -

F = \$\dfrac{1}{2\pi\sqrt{LC}}\$

But with stray capacitance and non-ideal inductors it'll be a little lower and probably align itself with 0.915 GHz very nicely. So it's resonant and it will behave like a low resistive impedance at this frequency - this will make the input port impedance look like 50 ohm if there is 50 ohm on the output port. In fact it will look like 100 ohm if there was 100 ohm on the output.

Note that there are two of these circuits in series but this doesn't alter things - the pair will resonate exactly the same.

And now the parallel tuned circuit. It's theoretical resonance is at 1.18 GHz but like I mentioned before, stray capacitance will lower this and given that the ground plane on the circuit board will likely offer great stray capacitance than it would to the series tuned circuits, I would be surprised if it didn't resonate fairly well aligned to 0.915 GHz.

At resonance, a parallel tuned circuit has infinite impedance and in practice (given inductor losses) I would expect it to look like a resistor of a few kohms in value.

In summary, in the operating band of 915 MHz, the network will be virtually transparent to the signal.