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The Google Pixel phone supports USB Power Delivery for fast charging and doesn't use any proprietary fast charging schemes. This means it should be able to work with other products even from Apple that support USB Power Delivery. 

From the USB Power Delivery negotiations, we can see how well the Google Pixel charges with the Apple 87W USB-C Power Adapter when the battery is fully depleted. When directly connected with a USB Type-C to Type-C cable, the Apple charger repeatedly advertises its power capabilities of 12 watts (5 volts @ 2.4 amps).

Several hard resets later, the Google Pixel then finally requests 12 watts (5 volts @ 2.4 amps) which is accepted by the Apple 87W USB-C Power Adapter.

The Apple 87W USB-C Power Adapter is also seen to follow up with two other power profiles of 27 watts (9 volts @ 3 amps) and 86 watts (20 volts @ 4.3 amps) in addition to the initial 12 watts (5 volts @ 2.4 amps).

We then observe that the Google Pixel requests 18 watts (9 volts @ 2 amps) from the Apple 87W USB-C Power Adapter which the charger accepts.

At a 0% battery charge level, we observe that the Google Pixel gets its initial charge at around 5 watts (5 volts @ 1 amps) but stops charging after 30 seconds. Charging then resumes in less than 10 seconds to happen at 13.5 watts (9 volts @ 1.5 amps). 

The USB Power Delivery behavior seen between the Google Pixel and the Apple 87W USB-C Power Adapter shows that charging actually works but the negotiations are far from being clean.