I noticed though, that since 2.16, the placement of TimeSignature is off in custom line-positions. I added an example to clarify this. Is this is bug or due to some new underlying mechanic?
\version "2.16.0"
\relative c''{
\numericTimeSignature
c2 d \time 3/4 e2. \time 4/4
\stopStaff
\override Staff.StaffSymbol #'ledger-positions = #'(0)
\override Staff.StaffSymbol #'line-positions = #'(-4 4)
\startStaff
c2\rest c\rest R1 \time 3/4 c2. c8 b a g f g
}