Digby, all the information I have says the Saxon Regts were designated Fusiliers in Prussian Service (as long as they lasted). The Regiments you brefer to are the ~16 'new' Regts raised by Frederick I believe, mostly from the new provinces (not exclusivly).

Infantry Regts (Fusilier)
1756 Battalion strengths of 700, which in Jan 1757 were augmented to approx 800.
2 Bns of 5 Fus + 1 Gren (100) Coys.
Gren Coys converged into Grenadier Bns during wartime.
No. 50 - 59 are Saxon Regts forcibly taken into Prussian service in Oct 1756.
No. 50 -53, 57-59 dissolved due to desertion within a year.
No. 54, 55 & 56. disbanded after 7YW
No. 49 (Diericke)created in 1758 from Pionier-Regt.

30 Inf Regt (Musketeer) Pritz, '57 Kannacher, '59 Alt-Stutterheim Pomerania
31 Inf Regt (Musketeer) Lestwitz Lower Silesia
32 Inf Regt (Musketeer) Tresckow Lower Silesia
33 Inf Regt (Fusilier) Thadden Glatz
34 Inf Regt (Musketeer) 'Prinz Ferdinand' Brandenburg
35 Inf Regt (Fusilier) 'Prinz Heinrich' -
36 Inf Regt (Fusilier) Munchow, '58 Alt-Munchow Pomerania
37 Inf Regt (Fusilier) Kurssel, '58 Braun Lower Silesia
38 Inf Regt (Fusilier) Brandes, '58 Zastrow Upper Silesia
39 Inf Regt (Fusilier) Jung-Braunscweig, '58 vacant -
40 Inf Regt (Fusilier) Kreytzen, '58 ALt-Kreytzen, '59 Gabelentz Lower Silesia
41 Inf Regt (Fusilier) 'Wied' Westphalia
42 Inf Regt (Fusilier) Schenckendorff Upper Silesia
43 Inf Regt (Fusilier) Kalsow, '59 Kalckreuth, '58 Bredow, '60 Zeiten Lower Silesia
44 Inf Regt (Fusilier) 'Jungkenn', '59 Hoffman, '60 Grant -
45 Inf Regt (Fusilier) Dossow, '57 Hesse-Cassel -
46 Inf Regt (Fusilier) Alt-Wurrtemberg, '57 Bulow -
47 Inf Regt (Fusilier) Rohr, '58 Grabow Upper Silesia
48 Inf Regt (Fusilier) 'Hessen-Cassel', '57 Beringer -
49 Inf Regt (Fusilier) 58 Diericke. Lower Silesia

50 Inf Regt (Fusilier) Oct '56 Wietersheim Ex Saxon Regt Rochow
51 Inf Regt (Fusilier) Oct '56 Wylich Ex Saxon Regt Bruhl
52 Inf Regt (Fusilier) Oct '56 Blankensee Ex Saxon Regt Garde
53 Inf Regt (Fusilier) Oct '56 Manstein Ex Saxon Regt Minckwitz
54 Inf Regt (Fusilier) Oct '56 Saldern Ex Saxon Regt Sachsen-Gotha
55 Inf Regt (Fusilier) Oct '56 Hauss Ex Saxon Regt Lubomirski
56 Inf Regt (Fusilier) Oct '56 Kalkreuth Ex Saxon Regt Prinz Friedrich August
57 Inf Regt (Fusilier) Oct '56 Jung Bevern Ex Saxon Regt Prinz Xaver
58 Inf Regt (Fusilier) Oct '56 Flemming Ex Saxon Regt Prinz Clemens
59 Inf Regt (Fusilier) Oct '56 Prince von Preussen Ex Saxon Regt Prinz Maximilian

Daryl