After reading the Legendary Item rules for mythic, I'm currently uncertain whether the user casts the spells, or the item itself:
Spellcasting: This item allows its bearer to cast a limited number of spells as spell-like abilities. This ability can be taken more than once. Each time it's taken, the bonded creature gains 5 points to spend on selecting what spells the item can cast. A spell costs a number of points equal to its level (minimum 1). The bearer can then activate the item to use each spell-like ability once per day. By spending double the cost, the bearer can use each spell-like ability three times per day. All spells must come from the same class's spell list...
So I cannot quite tell whether the character or object gains the spell-like abilities. From repetition, I would assume that it is the bearer.
The main reason I ask is that being able to cast spell-like abilities with the item would mean that one could qualify for prestige classes and feats with this ability quite easily.
I would also assume it's the bearer because allowing for an item to cast spells would let you really break action economy with two spells every round