grammar - Does the 助動詞「ます」 still have a 連体形 in modern Japanese?

Does the 助動詞「ます」 have a 連体形? According to 大辞林, it's ます, and I see the old forms ます／まする on 学研全訳古語辞典. However, in the comments on this question, Darius Jahandarie wrote the following:

@snailplane That link does suggest that ます has/had a 連体形. Relative clauses (which is the only place you would employ 連体形) definitely does not permit ます on verbs -- why this is the case I am not entirely sure, especially with ます having a historical 連体形. This sounds like an interesting question that should perhaps be forked off.

I've also found an answer on 知恵袋 suggesting it does, as in the examples:

1. 先生がおいでになりますときに


2. 式が開かれますところで、

However, Darius Jahandarie appears to suggest it might be "historical" rather than part of the modern language. If the 連体形 only appears in relative clauses and ます is considered ungrammatical in this position, doesn't that mean ます no longer has a 連体形?

It seems like one of these pieces of information must be incorrect. How can I make sense of this conflicting information?

Answer

First, I disagree with Darius Jahandarie’s claim that relative clauses are the only place where 連体形 is used. As fefe commented, …ますので is very common, and the connective particle ので attaches to the 連体形 form of a verb or an adjective, which means that the ます in …ますので should be considered as the 連体形 form.

Next, it is true that the use of ます in a relative clause is often old-fashioned. In modern Japanese, we usually use polite forms at the end of a sentence and before a connective particle, and not at the end of a relative clause. However, I think that it is an overstatement to call the use of ます in a relative clause “historical.” As you can see, there are many examples of such uses. Here are some more examples:

In a tourist bus, it is common for a tour guide to say something like

右手に見えますのは、富士山でございます。 You can see Mt. Fuji on your right.

In this case, it is more like a fixed phrase, and it would be strange to replace 見えますのは with 見えるのは.

In a department store, there is often a sign which reads:

このエレベーターは従業員が利用することがありますことをご了承願います。 This elevator is used also by employees. Kindly excuse us for any inconvenience.

(Glancing at the examples in the question and the examples which I wrote here, I noticed that in these examples, the nouns modified by the relative clauses containing ます are semantically light: とき, ところ, の, and こと do not have much semantic value. But I am not sure whether this is just a coincidence or it is a general tendency.)