If you post a stock transfer from plant A to plant A then there is no valuation. If you post a stock transfer from plant A to plant B then there might be a valuation. It depends on how each plant is valuated.
Movement types 557/558 were introduced by note 389484 to correct the stock in transit. They are derived from the class of the scrapping movement types 551/552 and they are used to post the stock in transit without purchase order reference.
Movement types 857 and 858 were introduced to handle the two-step transfer scenarios with gain/loss posting. Please check note 750311 for a detailed explanation. These movements were copied from core movement types 557/858 and they are only working with MIGO and not MB* transactions.
Movement types 851/852 have been developed to support the handling of In-Transit stock for the IS-OIL Transport and Distribution component. Please check note 312871.
Instead of 557/558 or 857/858, we would recommend to use the movement types 851/852 (GI Scrapping Transit/RE Scrapping Transit) to scrap the stock in transit. There will be an accounting document posted.
the stock in transit MARC-TRAME is valuated in MBEW in case the material is valuated. Generally the stock in transit is valuated in the receiving plant. There is no separate field it's cumulated with the other stocks in field MBEW-LBKUM.
If you post a 557/558 for a valuated material also a FI doc will be created and also MBEW will be adjusted.
Related SAP Notes/KBA
750311 - IS-OIL Two-Step Transfer: Upgrading to ECC 6.0
312871. - IS-OIL: Support of IS-OIL In-Transit stock with MT 851/852