〜のことだから ：〜という特徴のある．．．だから．．．（〜と予想される） Since it's (someone who...), therefore it is natural to have (someone)....
〜ことから ： 〜という理由で Since ....
so wait, is this like の then こと and then （だ）から？ like the thing of the subject and then dakara? Is that what this is like but contains a meaning of 'as usual'?
My grammar book, 500 Essential Japanese Expressions: A Guide to Correct Usage of Key Sentence Patterns, has [のことだから], [ことだから], and [ことだ] meaning the same thing: [なのだから].
When I took JLPT 2級 they tested the difference between [ことから] and [ことだから]. It is quite easy to mix them up.
This came up several times in something I was translating. I translated "a-san no kotodesukara..." as "It's a-san so...". It seems more natural than saying "A-san as usual...". For example in the example sentence above saying "It's Hiroko so she'll be late" or "Since it's Hiroko she'll be late" might be more natural.
This entry should be combined with the entry of " kotodakara" since it is the same.
I agree with kryptolusさん。 " Since it's Hiroko (who always late), therefore it is natural to have her late (this time around)."