Ok, I investigated this a bit on my private server. Worn haste over 127% will not work.
Here is the relevant code:
bonuses.cpp - line 293
//FatherNitwit: New style haste, shields, and regens
if(newbon->haste < (sint8)item->Haste) {
newbon->haste = item->Haste;
}
Since the haste value is a signed 8 bit number, anything over 127 is a negative number and will not be applied.
I checked this file back to June 2009, and it has always been that way. I would assume that if it ever worked it was due to custom code that is different from the eqemu sources.
Haste is also hardcoded to be capped at 100% for the sum of item haste, spell haste, and spell haste v2. Spell haste v3 is added on top of that. Allowing haste past 100%, excluding haste v3, would need to be done with custom code.