To avoid having to search through this multi-page thread, here is the crucial info contributed by several of the BA posters on this board. The full list of MF operated routes is as follows:

Updated 14 JAN 2020

Longhaul
Abu Dhabi (AUH)
Abuja (ABV) Moves WW > MF 01APR
Amman (AMM)
Atlanta (ATL)
Austin (AUS)

Baltimore (BWI) Moves WW > MF 01 APR
Bangkok (BKK) Moves MF > WW 01APR
Beijing (PKX)
Beirut (BEY)
Boston (BOS) - BA238/9 only
Buenos Aires (EZE)
Cairo (CAI)
Cape Town (CPT)
Chicago (ORD) - BA294/5 only until 31MAR. BA296/7 from 01APR
Delhi (DEL) - BA143/142 only until 31MAR. BA257/6 from 01APR

Denver (DEN) Moves WW > MF MAR only

Doha (DOH) Moves WW > MF 01APR
Dubai (DXB) - BA108/9 only. BA104/5 moves MF > WW 01APR
Durban (DUR)
Grand Cayman (GCM)

Hong Kong (HKG) - BA31/32 only Moves WW > MF 01APR
Houston (IAH)

Hyderabad (HYD)
Johannesburg (JNB)
Kuala Lumpur (KUL)

Kuwait (KWI) Moves WW > MF 30MAR
Las Vegas (LAS)
Los Angeles (LAX) - BA280/281 only
Miami (MIA) - BA208/9 only. BA206/7 moves MF > WW 01APR
Moscow (DME/SVO)
Muscat (MCT)
Nairobi (NBO) Moves MF > WW 30MAR
Nassau (NAS)
Osaka (KIX)
Phoenix (PHX)
Pittsburgh (PIT)

Portland (PDX) New to MF
San Diego (SAN)
San José (SJC)
Santiago (SCL)
Seattle (SEA)
Seoul (ICN)
Shanghai (PVG)
Singapore (SIN) - BA15/16 only
Sydney (SYD)
Tel Aviv (TLV)
Toronto (YYZ)
Vancouver (YVR)

Shorthaul
Aberdeen (ABZ)
Barcelona (BCN)
Bastia (BIA)
Belfast City (BHD)
Bologna (BLQ)
Brussels (BRU)
Bucharest (OTP)
Budapest (BUD)
Chánia (CHQ)
Copenhagen (CPH) Moves EF > MF 30MAR
Corfu (CFU)

Dalaman (DLM) New to MF
Dublin (DUB)
Düsseldorf (DUS)
Faro (FAO)
Frankfurt (FRA)
Gothenburg (GOT)
Hamburg (HAM)
Helsinki (HEL)
Ibiza (IBZ)
Kalamata (KLX)
Kos (KGS)
Kraków (KRK)
Larnaca (LCA)
Las Palmas (LPA)
Leeds\Bradford (LBA)
Lisbon (LIS)
Ljubljana (LJU)
Luxembourg (LUX)
Lyon (LYS)
Madrid (MAD) - BA460/461 only
Manchester (MAN)
Milan-Linate (LIN)

Montpellier (MPL) New to MF
Munich (MUC)
Mykonos (JMK)
Olbia (OLB)
Palma (PMI)

Perugia (PEG)

Podrodica (PGD)
Reykjavík (KEF)
Rhodes (RHO)
St. Petersburg (LED)
Santorini (JTR)
Split (SPU)
Sofia (SOF)
Stockholm-Arlanda (ARN)
Tenerife-South (TFS)
Vienna (VIE)
Zagreb (ZAG)

Key:
New route
Route move to MF
Route move from MF