I never went to Claremont in the '90's but I have been walking around Nedlands and Claremont at night recently and, even though it was only about 8pm at night it was still really creepy - especially around Karrakatta Cemetary! I'm actually glad, in a way, the girl who was raped in that cemetary had her head covered because if she could have seen the gravestones all around I think she would have had a heart attack.
I'm seeing ambush as very likely. Claremont is very dark at night and the main street, (Stirling Highway) is just all businesses which are dark and deserted in the middle of the night (and even moreso way back in the 1990's when Perth was still just a 'big country town' compared to other cities like Sydney and Melbourne. Also, back then, Perthites really deserted the nightspots as soon as midnight hit so the place would have become devoid of most humans pretty quickly after 12.
There are many, pitch-black spots where a woman could be snatched and stuffed into a car by a broad-shouldered man, very easily, I think...as evidenced by the Rowe Park attack.
It's possible the CSK felt that the 'ambush them and stuff 'em in the car' (Rowe Park) technique was too risky so he then may have tried to charm or trick them into the car (to avoid the possibility of a struggle being seen or heard). If that didn't succeed then he may well have resorted to what many kidnappers have done and that is, drive further up the street and park until the girl approaches and then jump out of the shadows, grabbing her. Or he may have circled around the block, driven up beside her and pulled her into the car.
I tend to think it would be less risky to anticipate where the intended target was heading and then drive up ahead and park out of sight then pounce on the girls' back as they pass you.
Just my opinion.