grammar - "[will] likely" vs. "[will] probably" in AmEng usage

As far as AmEng goes, can likely be an acceptable alternate to probably in the following OUP quiz?

1. The traffic is terrible so I'll probably be late this morning.




2. Climate change is likely to affect us all by the end of the decade.




3. I'll call them if you like, but they aren't likely to be in.




4. The concert tickets are likely to sell out very quickly.




5. I'll probably find out if I've passed or not by the end of the day.




6. You've probably heard this joke before, but I'll tell you anyway.

LIKELY

adv. Probably: They'll likely buy a new car soon. [AHDEL]

Usage:

Likely as an adverb is preceded by another, intensifying adverb, as in it will very likely rain or it will most likely rain. Its use without an intensifier, as in it will likely rain is regarded as unacceptable by most users of British English, though it is common in colloquial US English. [Collins]

likely meaning “probably” is often preceded by a qualifying word: The new system will quite likely increase profits. Some usage guides maintain that such a qualifier must always be present. However, likely without the qualifier is standard in all varieties of English: The new system will likely increase profits. [Random House Kernerman Webster's College Dictionary]

FOD

Answer

In examples 2-4, likely is a predicate adjective, appearing with auxiliary be: is likely, are(n't) likely.
Probably is always an adverb, so it can't substitute for a predicate adjective.

That leaves 1, 5, and 6, where likely can substitute for probably. Both are adverbs, and both occur after the first auxiliary verb (will likely, have likely), which is normal and common.

However, an auxiliary verb is not necessary; likely occurs with simple verbs as well:

• He likely slipped on the steps and fell.


• This likely has nothing to do with it, but ...

In effect, in American English, likely is a 2-syllable adverb complementing a 3-syllable probably.