Is Jesus speaking in Isaiah 40-48? In Isaiah chapters 40-48 there are several different titles for God, for example Creator, Redeemer, Savior, The First and the Last, King of Israel. After considering these titles I came to the conclusion that God in these chapters was referring to Jesus Christ and not God the Father because they all match titles given to Christ and never specify the father. What evidences are there of Jehovah being Jesus Christ in these verses, and what evidences are there against it? Answers from believers in the trinity, or not are both welcome.
The answer to your question is a qualified yes. If we are to accept that all Scripture is inspired by God, then we can logically deduce that Jesus gave these predictions to Isaiah to write. Whether or not those exact words are the utterances of a pre-incarnate Jesus or not is not worth arguing in that they are so accurate that whether they came from Isaiah or from Jesus they are predictive of him. 

Isaiah gave the most and the most accurate predictions of Christ of all the Prophets, however; much of his writings were to bolster the spirits of those exiles to Babylon, and even those prophesies concerning Christ were given to show that God would not abandon his people.

This excerpt is from the commentary known as the ‘Treasury of Scriptural knowledge.’


  Isaiah has, with singular propriety, been denominated the Evangelical Prophet, on account of the number and variety of his prophecies concerning the advent and character, the ministry and preaching, the sufferings and death, and the extensive and permanent kingdom of the Messiah.  So explicit and determinate are his predictions, as well as so numerous, that he seems to speak rather of things past than of events yet future; and he may be rather called an evangelist than a prophet. 


In addition the following will help in understanding Isaiah’s prophesies when compared to the Gospel accounts and come from the same source:

(Compare Isa_7:14 with Mat_1:18-23, and Luk_1:27-35; see Isa_6:1-13; Isa_9:6; Isa_35:4; Isa_40:5, Isa_40:9, Isa_40:19; Isa_42:6-8; compare Isa_61:1, with Luk_4:18; see Isa_62:11; Isa_63:1-4); his miracles (Isa_35:5, Isa_35:6); his peculiar character and virtues (Isa_11:2, Isa_11:3; Isa_40:11; Isa_43:1-3); his rejection (Compare Isa_6:9-12 with Mar_13:14; see Isa_7:14, Isa_7:15; Isa_53:3); his sufferings for our sins (Isa_50:6; Isa_53:4-11); his death and burial (Isa_53:8, Isa_53:9); his victory over death (Isa_25:8; Isa_53:10, Isa_53:12); his final glory (Isa_49:7, Isa_49:22, 33; Isa_52:13-15; Isa_53:4, Isa_53:5); and the establishment, increase, and perfection of his kingdom (Isa_2:2-4; Isa_9:2, Isa_9:7; Isa_11:4-10; Isa_16:5; Isa_29:18-24; Isa_32:1; Isa_40:4, Isa_40:5; Isa_42:4; Isa_46:13; Isa_49:9-13; Isa_51:3-6; Isa_53:6-10; Isa_55:1-3; Isa_59:16-21; 60; Isa_61:1-5; Isa_65:25); each specifically pointed out, and pourtrayed with the most striking and discriminating characters.  It is impossible, indeed, to reflect on these, and on the whole chain of his illustrious prophecies, and not be sensible that they furnish the most incontestable evidence in support of Christianity.

I have highlighted those verses which are contained in your question, but It is well worth taking the time to study Isaiah in relation to the Gospels.