What steve said *points up*.
The arcane polymorph/shapechange have unique qualities for each creature type only, but nothing selectable (like the red dragon's breathweapon, or the iron golem's gas attack)
Only the Druid and Shifter natural Wildshapes have abilities usable while transformed.
I always thought this a bit odd, seeing as how it is said that the spells use magic to change you. And through that change, you become 'exactly' what that creature is, including switching subraces and losing all equipped item bonuses.
If a character has 'become' a different creature 100%, by magic or no, they should have access to the creatures natural abilities.
It's probably a balancing issue i guess because a wizard will be able to turn into some pretty powerful things very quickly(not counting a whole variety of spell buffs), while the druid must wait longer to do the same, but will get creature features too.
Or bioware got lazy*shrugs*
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