Had no issues getting my Pom meals heated up on united in J SFO-NRT and NRT-SFO. I found a profound difference in response based on how you ask. Originally I would start explaining the situation about kosher and why I brought my own meal before the ask to have it heated. Now I simply walk to the kitchen as I board and request that they heat my meal along with the kosher meal they plan to serve. Goes over much better as most FA's simply don't understand why. Just tell them what you expect, and it goes over with no issues.
So, funny story...
15 minutes into the flight, the purser comes over and (in the most polite friendly Japanese attitude) begins to tell me that it's against the regulations, blah, blah. She is very apologetic. I explain that the meal they have for me is quite poor and I have done this before...
She responds that she will go and convince the FA to heat it up this time. She advised me that i should consider not bringing this in the future.
She comes back a minute later and tells me that she could not convince the FA to heat it up with the other meals in the oven. But she would heat it up after in its own oven. My packing skills were weak, and I think the fact that it was leaking a bit freaked her a bit.
When the meal came, the regal meal had pasta as the "main dish" that's it, just dry pasta. No chicken, just pasta. It was a joke. When they brought me my pom Sino steak a few minutes later (which was piping hot and awesome btw), I showed the purser exactly why I bring my own meals.
As a side, it's really shameful that on these new Polaris flight, they only offer this junk. Shameful!