"since implemented" is correct and can be used in written English.
You can use this phrase when referring to something that has been put into effect or started to be used at a certain point in time. For example, "Since implemented, the new safety regulations have significantly reduced the number of workplace accidents."
He has since implemented a policy that no actor may play more than five roles at a time.
Law-enforcement agencies around the world have since implemented their own data-driven approaches to tracking and adapting to crime trends.
The trust said it has since implemented a new IT system, retrained staff and holds daily reviews of all patients who miss cancer appointments.
France took the lead in pioneering the Unitaid air ticket levy, and was subsequently followed by a number of other countries that have since implemented the tax.
It has since implemented a company-wide, anti-corruption compliance program and now demonstrates "a commitment to designing and funding a meaningful compliance program".
YouTube has since implemented so-so anti-piracy protection through AudibleMagic.
The president's statements and the indictments support the many steps we have taken with the N.F.L. Players Association since implementing a comprehensive program of steroid testing, discipline and education.
The government says in the four years since implementing the regime, it has saved the welfare system $12bn it would have otherwise had to spend in the future.
We've been able to visit 9% more people in the field since implementing this new technology, which equates to an extra 14,000 home visits each year.
Since implementing its global manufacturing principles in 1997, Mattel has dropped several dozen suppliers and licensees for chronic noncompliance; the company budgets about $10 million a year for internal and external monitoring efforts alone.
While we have confirmed that no Xerox branded products have been sourced from APP since implementing our ban in 2002, we have uncovered that a Xerox European entity bought and resold APP branded paper as recently as 2011.
