Is it possible to use Full Text Search (FTS) with LINQ?

Yes. However you have to create SQL server function first and call that as by default LINQ will use a like.

This blog post which will explain the detail but this is the extract:

To get it working you need to create a table valued function that does
nothing more than a CONTAINSTABLE query based on the keywords you pass
in,

create function udf_sessionSearch
      (@keywords nvarchar(4000))
returns table
as
  return (select [SessionId],[rank]
            from containstable(Session,(description,title),@keywords))

You then add this function to your LINQ 2 SQL model and he presto you
can now write queries like.

    var sessList = from s   in DB.Sessions
                   join fts in DB.udf_sessionSearch(SearchText) 
                   on s.sessionId equals fts.SessionId
                 select s;