Actually, as a non-native speaker of english, my experience is precisely the reverse. Being unable to understand the odd word or colloquialism is most of the time not an issue. Often, the context will supply the meaning or likely meaning and even if it does not, it usually does not prevent understand the gist of what is said. Where it gets really difficult is where you are faced with a flow where you can't even identify where one word finishes and another one starts. That is where things start to be much more challenging. Although not directly relevant in relation to announcements, this is also true in a one-to-one conversation. If there is a word you do not understand in what your interlocutor says, it really is not an issue as a non-native speaker to ask him or her to explain what the term means. If it is the whole sentence that you struggle with because of an accent that you are unfamiliar with, you can of course ask them to repeat but, more often than not, you are none the wiser after the sentence is repeated and you are also conscious of the potential to offend them by repeatedly asking. So, instead, you tend to smile and pretend that you have understood even when you do not have a scooby what it is that they mean.

It tends to grate on my ears too but these are good examples of usage that is rather unlikely to phase a non-native speaker. Most basic speakers of English will be familiar with reflexive pronouns and will know that "myself" refers to the person speaking. So you can easily work out what they mean when they say "speak to myself", however incorrect it might be."Deplane" is not particularly difficult to understand given the context. This is the kind of work you do all the time in a language that you only have a limited knowledge of. You tend to guess what the intended meaning probably is given the context and "deplane" would not normally be that difficult to work out if you know what a plane is and what the prefix "de" usually indicates in English, which many speakers with a basic working knowledge of English would do (and certainly most Romance language speakers would).