You can apply class abilities to spell casting from magical items
While casting from an item is not the same as a Casting a Spell action, it is still casting a spell. Unless a term is given a special definition in 5e game terms, you use the common definition for that term. You are casting the spell, the ability to do so comes from the item. For instance, the Staff of Fireballs:
.. you can use an action to ... cast one of the following Spells ...
Is no different, in this regard, to Wand of Fireballs from:
you can use an action to ... cast the Fireball spell ...
Jeremy Crawford has posted a number of answers we can point to in the time since this question appeared that verifies this really is the case. Each time he's been asked about a specific class ability the answer has been an affirmative. These were made when his tweets were official rulings, but since have been "downgraded" by the Sage Advice Compendium to his personal advice and perspective. While this is true, it still is clarification of the intent of the designers.
Metamagic
Can Metamagic be used on magic item casting a spell? Yes.
If a magic item's description says you cast a spell from it, you can use Metamagic on the spell. #DnD
and
Metamagic works w/ any spells that sorcerers cast. Wild Magic Surge can work w/ any sorcerer spell they cast. #DnD
Wild Magic
Can using a magic item cause a Wild Magic Surge? Yes
Yes.
Arcane Ward
Can casting from a wand/staff recharge Arcane Ward? Yes
Arcane Ward/Twinned Spell works when you cast a qualifying spell. It even works when an item says you cast one. #DnD
I don't know if it is awkward to answer my own question but after my last game, i now have a more plausible answer in general, just sharing it here for future reference :
Most of the spells that an Eldritch Knight uses in thick of battle, does not require material components thus making the need for a foci redundant and having war caster feat feasible for shield bearing EKs using war magic class feature without further mingling with RAW weapon switching or tiny/wearable foci etc.
A happy ending!
Edit : For a workaround to this problem Apocalisp's answer is better within RAW.
Those of you who like house-ruling can modify EK's bond with it's weapons to count as arcane focus to specifically bypass this problem.
Best Answer
Yes. Magic items in the DMG refer to mundane items listed in the PHB, and use the corresponding stats. Staffs, rods, and wands are listed in the PHB as categories of Arcane Foci, therefore anything listed as one of these types of items in the DMG is referring to an Arcane focus unless otherwise stated.
If you were to assume that items in the DMG do not correspond to the stats listed for them in the PHB unless explicitly stated, you would have to assume that all armor, shields, and weapons in the DMG have ambiguous stats. That would mean that all of these items are not actually armor or weapons unless explicitly stated, which is absurd.
Some items are explicitly listed as arcane foci, such as the Tome of the Stilled Tongue. This is because they are an item type that is not listed in the PHB as an arcane focus.