You can to some degree, but the true DX7-FM setup cannot be replicated.
On the DX, for the tines sound, the six operators would be set up into three sets of two. One set made the basic main sound, the second was the higher harmonics of the main sound (and would provide the "growl" when played harder) , and the third was the percussive hammer part of the sound. On the P-12, there are four operators (oscillators + Envelope) at most. So, it cannot set up a six operator patch. There are work arounds. In the DX, each operator was a sine wave. Two sines modulated together would create a complex wave and often the wave for a "musical" sound was near a saw or square wave. So, potentially an oscillator on the P-12 can do double duty since it can create a complex wave on its own near the modulated sound of the two sines on the DX. Thus, three or four complex oscillators could theoretically mimic a six operator FM system.
What was especially disappointing was lack of high frequency sidebands when modulating the P-12 oscillators together. What gives the DX the real sparkle is the sidebands it creates in the 6k hz + range. The P-12 was simply not capable of producing those sidebands. Granted, I was only using sines on the P-12 for modulation. I haven't tried it with the more complex waves. So, it may be possible to get the sidebands going that direction. However, the two sines should be able to put out those high frequency sidebands. I shouldn't be having to do work arounds for such a basic FM operation.
However, don't take this as saying the P-12 is an inferior instrument. It isn't. It is a blast! Here's a later piece I put together, primarily P-12 (both melodies), Pro-2, DX-7 and P-08. Each one of the instruments has its own palette of colors and they blend so well.
https://soundcloud.com/jdt9517/2017-02-19-waltz As a result, the DX-7 is still alive and well in my studio. The only thing that may take its place is a Yamaha Montage - but that's an expensive proposition and I don't see me doing it in the near future.