Sure can with a couple of extra lines...
Code:
menu nicklist {
  -
  Search
  .#: search # $1
  .Log file...: search @file $1
}
menu channel {
  -
  Search
  .#: search # $?="Search key:"
  .Log file...: search @file $?="Search key:"
}
alias search {
  window -k0z @SearchResult -1 -1 $calc($window(-2).w * .75) $calc($window(-2).h * .75)
  var %fi = * $+ $replace($2-,$chr(32),*) $+ *
  if $1 == @file { 
    var %fn = " $+ $sfile(*.log) $+ "
    if $isfile(%fn) { filter -fwcp %fn @SearchResult %fi }
  }
  else { filter -wwcp $1 @SearchResult %fi }
}