From AC point of view, power planes are identical with ground planes. Of course, some rules must be obeyed, depending on your design. Both planes are return paths for high speed signals routed on signal layers. The return path for high speed signals is the path with the lowest impedance, more precise the plane under the trace. In a 4 layer board, assuming that top and bottom are routing layers and middle 1 and 2 are power/gnd planes, when you jump with a trace from top to bottom, you will create a discontinuity in the return path. The return path for portion of trace routed on top layer is the plane under it, and the other plane for the bottom portion of trace. But the planes are not connected (from ac point of view) in the vicinity of the via used for jump. To compensate that discontinuity, place a decoupling capacitor in the immediate vicinity of via. More informations available at mcu server or in e-books up/dl section (keywords: signal integrity, high speed pcb).
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