Some people might agree with me and some wont but just look at the evidence:
1. He implanted the Hougyoku in Rukia even though he as a previous Captain should have known she would be brought back to Soul Society. And why would he risk that when he had managed to hide it in the real world for all this time.
2. a) If Urahara hadnt sent Ichigo to Soul Society Rukias execution would have gone through, revealing that the Hougyoku was buried within her soul. And because Ichigo and friends hadnt caused such a commotion the execution would have been witnessed by all the captains preventing Aizen from sneaking away like he did.
2. b) Rukias Execution would have been prevented by Kyōraku and Ukitake but they would probably be killed in the process and Rukia would be captured again or killed.
3 The reason Orihime could be captured was because Urahara implied she was useless and that led her to train with Rukia in Soul Society. And if she hadnt been traveling between worlds Ulquiorra would not have been able to capture here that easy. Bleach 233 page 18 | One Manga
I do not think that Urahara is working with Aizen but rather letting Aizen think that he is pulling all the strings when in reality Urahara is the true puppet master.
Aizen may be the Devil but Urahara is the Eddy