Any update on the reason they were denied entry?

If these overlanders have problems with COMS, and are back in Freetown, surely they must have access to the internet !

I was planning on heading this route same direction or vice verse.

Also, has anyone been held back to be quarantined ??

'Quaratined'? If you are referring to Ebola I am pretty certain this has got nothing to do with the situation for these particular travellers. See here:

WHO | Liberia and Guinea discharge final Ebola patients in latest flare-up and begin 42 days of heightened surveillance

I also speak from experience as we took a group of 17 across the border back in November 2015 and another group of 14 over the border in March 2016 both times without too much drama.

I was in Sierra Leone a few months back working with humanitarian NGOs. Post -ebola control measures are a bit of an obsession with the SL government at the moment. There have been isolated cases reported in Liberia since the outbreak ended and each time this occurs, the government reacts...and blames Liberia. I suspect the border closures are part of a diplomatic spat between the two.