Is it ever right to use ば conditional to mean 'when'?

Question

「だっ大丈夫よ、まるちゃんだってわたしたちのタイプだと思うよ、ねぇ」ととし子ちゃんがなぐさめれば、「そうだよ。さくらはぼくらの方の仲間だよ」と長山君が笑顔で言い、「そうよ」とたまちゃんが優しくうなずく。
(When?) Toshiko comforted her, saying, "It's alright. I think Maru is our kind of person", Nagayama smiled, saying "That's right Sakura is on our side" and Tama amiably nodded her head in agreement.

I've only ever seen the ば form used to mean 'if' rather than 'when'. But 'if' certainly doesn't make sense here. How should I interpret なぐさめれば in this context?

Edit: I understand that in general the distinction between 'when' and 'if' is a bit blurry in Japansese, but I was under the impression that the ば form always meant 'provided that...'. The 'when' in this sentence seems to be a definite 'at/after this point in time something definitely happens'. There doesn't seem to be any hint of a conditional in it. I would have thought とき would have been better here. I must be missing something.

Answer 1

From スーパー大辞林:

ば

③ […] 引き続いて起こる事柄についての，きっかけを表す。…すると。

If I may add more to the quoted definition, this is a particular type of 〜ば where it denotes the chronology of a single occurrence (trigger event → following event), and says nothing about what would happen if the trigger event were to happen again. To me, this kind of 〜ば seems more common in written language, and less likely to be found in spoken language.

The natural translation can either be “then” or “when”, depending on the context or clause order, e.g. X happened then Y happened, or Y happened when X happened.

Some examples from published books, found on 少納言:

• はっとして見渡せば、ほかにも植物が並んでいます。
  Startled, I looked around, then saw other plants as well.
• 聞けば、この教授の学生時代の同級生が例の人事部の佐藤次長であるとのこと。
  When I asked, I was told this professor's classmate was that assistant manager Sato from HR.
• 東京に出れば、私の生まれ故郷に足を向けることも多くなった。
  After coming out to Tokyo, I've been visiting my hometown quite often.

Answer 2

To add two things:

1) The if/when blurriness remains even when they use 時, believe it or not.

もし彼がきた時は、どうにか対処しなければならない。If he does wind up coming, then we'll have to deal with that somehow.

2) Another thing to keep in mind is that ～もなければ、～もない is a fixed phrase meaning there is none of either one thing or the other.

小説もなければ詩集もない does not mean "if there are no novels, then there are no poetry collections." It means "There are no novels and there are no poetry collections." It's a more emphatic form of 小説も詩集もない.

Answer 3

The English 'when' versus 'if' distinction of 'probably going to happen' versus 'maybe not going to happen' is something Japanese on the whole doesn't bother with. There are certainly cases where using one conditional form sounds more tentative than another, and contexts that make tentativeness clear for other reasons; but none of the conditional forms (ば, ったら, と, etc) explicitly state that the condition they're referring to is either likely or specifically not likely. You can add a degree of tentativeness by using もし (もしやれば sounds a lot less like it will happen than just やれば), but beyond that, there's no explicit likeliness involved.