\version "2.19.83"

%%%% David Nalesnik's metronome-mark-alignment function:

#(define align-tempo-with-accidental
   (lambda (grob)
     (let* ((p-col (ly:grob-parent grob X))
            (sys (ly:grob-parent p-col X))
            (all (ly:grob-object sys 'all-elements))
            (grob-name (lambda (x) (assq-ref (ly:grob-property x 'meta) 'name)))
            (pl (filter
                 (lambda (x) (eq? 'AccidentalPlacement (grob-name x)))
                 (ly:grob-array->list all)))
            (pl-p-col (filter
                       (lambda (x) (eq? p-col (ly:grob-parent x X)))
                       pl)))
       (if (pair? pl-p-col)
           (let* ((accs (map cadr (ly:grob-object (car pl-p-col) 'accidental-grobs)))
                  (X-exts (map (lambda (x) (ly:grob-extent x sys X)) accs))
                  (un (reduce interval-union '() X-exts)))
             (car un))
           ; Return the default.
           self-alignment-interface::self-aligned-on-breakable))))

%%%% Tiny example:

music = { cis'1 }

<<
  \new Staff { \music \music }
  \new Staff { \music \tempo "Tempo" \music }
>>

\layout {
  \context {
    \Staff
    \consists "Metronome_mark_engraver"
    \override MetronomeMark.X-offset = #align-tempo-with-accidental
  }
}