Can H264 achieve "equivalence" with ProRes 422? Has anyone done or seen any tests comparing Apple ProRes 422 with high-bitrate H.264?

We use 422 as a delivery format to go to DCP for theatrical versions of trailers.
The bitrate is around 150mbps.

We are wondering if it is possible to reach adequate quality with H.264. Say, with bitrates of 50-100mbps, and tweaking the GOP size/structure. (E.g., only using "I" frames.)

Assuming H264 is a more "efficient" codec, we are hoping to get smaller file sizes.

Or does H.264 just not have the color depth to compete?

It would be great to see if someone has done some real-world testing.

Update 1: I just did a quick test using 50mbps, GOP size 1, I-frames only ... and "by eye" I see no difference whatsoever. Same level of noise, same colors. The ProRes is 1.92GB, the H264 is 566MB. How would one "test" the difference technically? Or measure the color information?

Update 2: I did some more testing ... with Adobe Media Encoder, using MPEG2, and the "4:2:2" profile, the ProRes file went from 1,920MB to 290MB! And I would say, subjectively, that is is 99% as good. This is remarkable. (With H264 I was down to 500-700MB)
Well going by the numbers h264 has a lesser bit-depth and color accuracy than ProRes 422. PR422 has 10bit and 4:2:2 chroma sub-sampling, h264 has 8bit and 4:2:0 unless you encode in the Hi422P Intra profile which isn't very well supported in the wild but offers 10bit and 4:2:2.
So in that case I don't think you will have any difference what so ever between the two formats but a better compression ratio than with ProRes.

E: If you want to go real ape shit you can also encode in the 4:4:4 Intra Profile, that supports up to 14 bit of color depth. So technically superior to ProRes4444. Though you probably wont find any commercial application that supports it.

On another note, I don't think content delivery for cinema should be done in h264 nor ProRes 422 especially when you plan to encode to a lossless codec (JPEG2000/DCP) afterwards. It just doesn't make much sense to do so, all you loose is quality even though there is no need to do so, you only save space until you encode your DCP. There are other good lossless codecs, that offer very good compression, to use before encoding the DCP.

You could for example go directly to DCP, the Adobe Media Encoder offers export to 2k DCP since CC 2014, you can skip an encoding step and have a lossless codec with very good compression ratio.

Another great intermediate codec is UtVideo aswell as Schrödinger (an implementation of the Dirac codec from BBC, its available through FFmpeg).

In the end though theory always differs from practice and if you don't deliver for nation wide cinemas with excellent projectors and what not, that quality difference in your delivery chain will be neglectable.
The only thing that could be pitfall is that h264 is very complex an by that always prone for some weird visual defects, so final inspection is always a necessity with h264.