Sounds about right! My knowledge on the exact dates and reasons isn't too good either because it was before I became interested in football - I just remember the ground being taken down and re-developed into a horrid modern housing estate with all the houses packed together!
Dunno what the arrangement is, but I think they share the ground with Leigh rugby league club (but I dunno who owns it). It's just a shame since obviously the RMI stands for Railway Mechanics Institute which is a very large, now mostly derelict (

) building which in its heyday was the second most important railway works in the country after Crewe, but now both the railway works and the football team have gone Horwich doesn't have much of its railway heritage left
Ironically of course, Bolton Wanderers have now wandered into Horwich (well, the outskirts) with the Reebok Ground so we do now have a football club again, just not one we can properly call our own!