How good are chances to score in the regionals for an F/O with 900+ TT (some airline time included)?
Depends on the person really.
I've interviewed and trained pilots who could fly circles around me but I could smell the BS every time they opened their mouths. I've also interviewed and trained other pilots who could not keep the airplane straight and level but were genuinely nice people, tried hard every day, and put everything they had into their improvement. This applies to pilots with 900 hours just as much as those with 9000 hours.
The airline I work for does have a matrix like that described by Mostly Harmless, but it's not a points-based system. It's either you have the minimum experience levels or you don't. If you do, you're generally given the chance to interview. Something akin to "it's your job to lose."
Because of this, we put a lot of stock into the interview process and the opinion of our current employees. I know one or two people who admitted to having a horrendous interview, but enough people within the company vouched for them and they were given a position. I also know of some really experienced pilots who interviewed well, but their internal references were not stellar or otherwise told a different story than the applicant was telling.
When I was hiring, I would ask myself one question of everyone I'd interview - would I enjoy spending 4 days with this person or would I rather gouge out my eyes with a rusty nail that had been sitting in a pig pen. If it's the former, you'd likely get the nod and I'd let training see if you were up to the task. If it was the latter, it would be a big, fat no. Most interviewers are easy to get along with when line flying, so if we don't think we'd want to spend a 4-day pairing with you, then the line pilot with very strong opinions of him or herself and the company will certainly let us know their feelings on the matter.
But what are your chances? If you meet the minimum requirements and have a good attitude, pretty good right now.