I can attest to the DC ticket collection agency removing the item from your credit report once paid. They removed mine in about one month.
Here is the quote from their website:
If I pay a ticket that has been listed with a credit bureau, will my credit file be cleared?Normal practice in the credit reporting industry is to retain a reported debt in history for a period of seven years, even if a debt is paid during this period. However, in the interest of our customers, we have requested the collection agency (Professional Account Management L.L.C.) to automatically send a delete record to the credit bureaus whenever a collections account has been paid in full. Therefore a record of your delinquent ticket debt should disappear from credit bureau records once the payment is received. As a record of payment is sent from the collection agency to the credit bureaus on a weekly basis, and because a record of your payment may need to be communicated to other credit reporting agencies which did not receive the primary listing, you should allow a reasonable period of time for all records to be cleared. All communication concerning the status of your tickets with credit bureaus should be directed to Professional Account Management, L.L.C. (866) 353-7145.
http://dmv.dc.gov/about/faq5.shtm
