The following should help with the latter part of your question, but I have no information on the high-altitude Spitfire unit or any record of the 4 July claim:
2.(F)/Aufkl.Gr. 123
[extracts]
June 1942: Staffel received 4 pressurized, high-altitude Ju 86 P-2s in late May/early June for use over Egypt due to the heavy losses in Ju 88s to RAF fighters. Later, the Ju 86 P-2 (or Ju 86 R-1 according to other sources) missions were flown along the Nile from Alexandria to Cairo, and along the Suez Canal from Port Said to Suez in August and early September 1942, and brought back photographic evidence of the huge build-up of Allied equipment and supplies, leading the Germans to the correct conclusion that Montgomery would soon be in a position to launch a major and perhaps decisive offensive in North Africa.
June 1942 – June 1943: two Ju 86s lost, one in combat and the other in a crash.
2 July 1943: Ju 86 (4U+IK) FTR from Alexandria, 100%, 2 MIA.
6 July 1943: Ju 88 D-l trop crashed at Athens-Tatoi due to engine failure, 100%, 4 killed.
8 July 1943: in a report up the chain of command on its high altitude capability, the Staffel stated it had 2 Ju 86s and 2 Ju 88Ts but that all four of these were unserviceable for various reasons and consequently the Staffel could not comply with an urgent Luftflotte 2 demand for high-altitude missions over Cyprus, Alexandria or Benghazi.
There is no further mention of 2.(F)/123 Ju 86 losses in the surviving documents.
Larry
P.S. According to the carefully maintained German loss records, the Staffel only lost two Ju 86s to the enemy, as you can see from this tabulation:
http://www.ww2.dk/oob/bestand/aufkl/b2ag123.html . 2.(F)/123 had the only aircraft of this type that would have been used for these long distance flights to Egypt. There were no others in the Mediterranean theater.