Shared via on 22pF cap only used to smooth differential clock signal?
lets model that.

Assume 1 nanoHenry per via.

Assume 200 picosecond edge. 

assume 1 volt swing (your voltage may vary).

The current thru 50 pF(both caps), with 1volt in 200 picoseconds, will be

I = C * dV/dT

I = 50pF * 1v/0.2 nanoseconds = 50/0.2 * pico * 1/nano = 250e-3 = 0.25 amps
assuming PCB foil inductance dies not limit current.

The rise and fall times of this current will be 1/2 of the voltage, or 100PS.

The voltage across the inductor (the GND upset) will be V = L * dI/dT

V = 1nH * 0.25 amps / 0.1 nanosecond = 2.5 volt.

So there will be lots of crosstalk; the gnd side of the shared caps, which is the top of the via, will be 2.5 volt.

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Another way to think is : what is reactance of 22pf ( or 50pf) at 2,000MHz?

since 1pf at 1,000MHz is 159 ohms, we know 22pF at 2GHz is 159/44 = 4 ohms.

While the 1nH inductor to ground is 12 ohms (2 * 2 * pi).

Thus we are guaranteed massive trace-trace crosstalk at 2,000MHz,