It's hard to tell what you're going after, since there's little description, but I assume you'd want it more like this to save two rows in your HasMany Through table:
array(
(int) 0 => array(
'user_id' => (int) 5
'solicitation_id' => '70'
),
(int) 1 => array(
'user_id' => (int) 6
'solicitation_id' => '70'
)
)